A Jackcident is when a male human is masturbating over erotic material, but accidentally cums at the moment that the camera is looking at the male porn actors face or there is no one but the male porn actors in shot.
1. Jim was enjoying a good bishop bash, until he jackcidented all over the place
2. Bob: I had such a Jackcident last night!
James: You're ahomosexual! Don't you deny it!
Bob: Seriously dude, it was a Jackcident!
accidentally upvoting a post on yik yak that you meant to downvote (and vice versa). Yakcidents suck because you can't undo a yakcident. Also used as yakcidental and yakcidentally.