To fail miserably at various things.
Examples of such things failed at are: video games, talking to women, and sexual intercourse. Basically life.
Also while having sex with someone, you call that person the wrong name (a name of a someone you had previous relations with).
The com puts an emphasis on the fail.
Guy 1: Dude you suck at video games. You are always dying...
Guy 2: Yeah I know, I know, I am a comfail.
Guy 3: Yeah you are.
Guy 1: Man I called her Tasha..... Her name was Emily
Guy 2: Dude that's a comfail and a half....
Guy 1: That halted any chances of sex after...