I'll take your definition of split this into two categories: Intentional and Unintentional.
Intentional trolling is to muck around, not be super serious and exasperate a situation with intent.
Unintentional trolling is to muck around, not be super serious, and not have knowledge of your actions; ignorance.
Example for intentional: Playing AP Tryndamere with pre-existing knowledge that there is a high percent chance your team will lose because of you.
Example for unintentional: Playing AP tryndamere becaue you saw a guide online making you assume it was highly viable.
Example of intentional: "Feeding" the enemy team because you got called out for playing poorly and you can't admit your mistakes
Example of unintentional: "Feeding" the enemy team because you got called out for playing poorly and didn't understand your mistakes.
The examples are very close and its kind of a gray area. If you're intentionally trolling you're just being an asshole for no reason and you know it. If you unintentionally troll you're skull is too thick for you to understand what you're doing.