The word you're looking for is "burst"

Stop using "one shot" to mean, "they killed me with their whole rotation very quickly." A real one-shot is actually something to complain about. Even an ultimate ability should not be able to kill a champion in a single attack. Base stats should be designed to prevent anyone from getting a kill with a single ability. But getting burst by an assassin or mage using all or three of their abilities, when they're designed to deal burst damage, is not. I really don't get why people are opting for the incorrect term when it takes longer to type.

Edit: I do want to address something from the comments. That part where I said base stats should protect you from a true one-shit only applies when you're the same or one level off, and about the same on items. A damage champion with 4 levels and 4 items on you killing you in one ability is, I think, perfectly fine.