I don't really get it since it depends so much on the situation. Like every Friday I perform for around a hundred people and most of them laugh very easily, and most of them like me and I'll have many sets where most of them laugh at every joke long and loud. But I don't usually consider that killing because its such a great crowd and they love me and the host does this awesome thing where he'll do a loud quick laugh a microsecond after the joke ends which encourages everyone else. But then when I go to an open mic in the city and there's 15 other comics and I'm doing my five good minutes and they're mostly giving audible laughs, I give myself more credit for that. I have low self esteem so it's hard to admit that I'm actually funny, but even I know I am. Despite this, I don't know what I would consider killing or if I even have, I'd say no. But then again how can I do better than 100% laughter on every joke? Not saying I've done that, probably no one has, but I've gotten close sometimes, so what should I be looking for to improve from those sets? Louder laughs, longer laughs, higher percentage laughing (that's still hard for me to tell)? How do you really determine you're "killing" if you don't know what criteria to set for yourself? I think some people have a lot of self-confidence and consider a set where they're doing what I'd be disappointed with killing, and some people are like me and consider a set with 80%+ laughter, loud and long laughs, etc. a good result but something to improve upon and therefore still a failure in a way. I'm sure the way to be is not on either extreme but none of the self-love techniques I've googled have worked for me and me talking shit about everyone who shows confidence behind their backs hasn't done much for them.

Anyway the venue should be a factor. When I do a good job on a late night show and comedy central calls me to do a half hour I'll say I killed, but that might never happen so I might never use the word in my entire career.