My definition is obviously very different than everyone else, since no one agrees with me when I say ADCs are broken and Zoe is fair.
To me, it means that there's a way to avoid the damage/CC/whatever, or mitigate it a bit, and win a fight regardless of stats.
So what does counterplay mean to you?
the retardedness of Zoe's w is the definition of no counterplay, complete RNG, pure luck, no skill. ( riot dont remove my message, i love you)
A counterplay begins at level 1, game start. You go in, take smart trades and kill your laner. Snowball off that and BUILD stats to further your lead
Tl;dr no real thing, just gameplay. Adcs are fine, zoe is fine, every champion is fine because they don't do damage if theyre 0-20 with 10 cs at 20 mins
Counterplay to me means something about a champion that can be punished or avoidable (skill shots and flash and sheit). Some champions (
& 
just recently) just seem to have way less counterplay than others and their kits are designed around a safe laning phase and getting ahead. When they do get ahead, the fun scale going against them drops to illaoi scale.
Something which adds an advantage to a fight but which can be counteracted by the opponent's actions is something that has counterplay.
's passive gives a strong shield which lasts, or at least lasted, a while, making her get a big advantage when trading with the passive up. But the shield falls to the ground on anything but a last-hit (which is in itself not guarenteed due to random minion aggro changes and server lag) and can be stepped on by her opponents. This is the counterplay of her strong shield.
's passive is similar, with its counterplay being to pop the shield with a weaker attack before using stronger ones
windwall, however, has much lesser counterplay, that being spells which circumvent the wall by 
coming from above or as an instant AoE spell. He's more vulnerable once its on cooldown, but by itself it gives him a free retreat to wait out the cooldown and a free offense without having to worry about taking damage back whenever it is up.
is an example of what happens when too much counterplay is added to a kit, making that kit wholly unreliable. As a burst mage, leblanc is easily outclassed by the likes of 
, or for an example of a better burst mage with counterplay in their kit, 
, who has strong burst but which is tied to manipulating her ball with skill shots. And as an assassin, she just doesn't work outright, having no execute mechanic and no mechanics to isolate and pick particularly important opponents. Instead she sits in an awkward middle ground of doing burst mage levels of damage on an assassin's delay with the ability to blink back after her combo.
Counterplay is much more important for high-damage characters, but as I demonstrated with Poppy, it can even have a place with tankier ones. 
early after his mini-rework is a good example of missing counterplay. His stretching strikes is a fun concept smashing two targets together, but it had, and still has, a problem in that he can miss his initial skill shot entirely and still start a chain of cc because the spell hit a minion behind you. Riot's answer to this was to nerf his damage and health drastically to the point that ALL he does is CC now, which still doesn't address the underlying issue.
Counterplay to me means....Riot's poor excuse to rework the entirety of the assassin class over one pathetic word.
Alright, making this a separate comment. Sorry it took so long to get back to this.
Counterplay is the ability to disrupt another champion's intended purpose, by that through champion picks, abilities, items, or gameplay strategy.
All champions have counterplay. The determining factor is how easy that counterplay is to understand and enact.
So, taking one of your favorite champions to complain about, Vayne. You say she has no counterplay, a sentiment that likely comes from not playing her, and the key to knowing how to fight against a champion is knowing how they work. I'm not a Vayne main by any stretch, but she is one of my more frequently played ADCs, and I understand her fairly well (both as and against).
Vayne is only single target damage, with zero influence outside of her auto attack range. She has no AoE spells, no ability to poke, nothing, not to mention that her largest damage spike requires her to sit on the same target for 3 attacks. So what does this mean? That she is one of the best duelist champions in the game, something that should never be dismissed. She has the ability to outplay a single opponent, but once you bring friends, that power disappears. If Vayne is a problem for you to deal with alone, then stop doing it alone. Any additional person makes her job infinitely harder, and the more you bring, the harder it gets (especially if you bring CC with you as well).
As mentioned before, Vayne has no effective range outside of her autoattacks, which makes her very easy to bully in lane (especially with everyone's lack of resistances). So do that. Punish her harder than a college student's liver after the weekend. Now, here's the very important part: being a weak laner does not mean that it is impossible for her to win lane. If you are also a similarly weak laner, or a host of other possibilities (enemy jungler champs your lane, misplay bad towerdive gets her a double kill, use your imagination).
This shitty late game is made up for with a shitload of damage come late game. Now, same rules still apply, poking her down will weaken her ability significantly, CC will destroy her, but be aware that Vayne is a ticking time bomb, same as any other hypercarry. If you allow the game to stretch to a point where gold differential no longer matters, than you will have a significantly harder time achieving a win.
So, TL;DR on how to counter Vayne?
Step 1: Don't 1v1 her. Remember the buddy system, and bring CC.
Step 2: Hit her as hard as you safely can in lane, to set her back as far as possible.
Step 3: End the game before she finishes her items, because at that point how bad laning was doesn't matter.
and a quick extra tip: BUILD ARMOR
Yes, Vayne deals true damage, but that is only on the 3rd auto, and only as an extra bonus. Every single other damage number she puts out is AD, so build the thing to counter AD.
when i think of counterplay i think of using things ingame to outplay people rather it be skill in dodging skill shots or a 
at a choke point and some cc for 
To me counterplay is the ability to win a fight based on your skill alone. If you need another player to help you, that's not counter play. But if you can beat someone on your own skills then you've outplayed them. Or if they dive you, you countered them. Zoe is fair, she can be avoided, I've seen zoe get destroyed as well as destroy. Adc's are the same. They can be stomped but they can also stomp. It's when someone, anyone, 1 shots you with something that is imposible to dodge or avoid that it's unfair and there are very few things like that in league.
