1) When a n00b thinks he pwned someone, but the kill took much too long, or was much too n00bish to be an actual pwn.
2) When 2 people are going for the same kill without knowing, and you think it was your kill until you see "(insert actual killer's name here) fragged (insert victim's name here)" or something of the like.
n00b: *after killing someone with MK-48* "Pwned!!1!11one"
not n00b: fauxpwn, n00b you emptied 100 mk rounds in the guy before he died...
guy 1: *lines up for headshot and fires*
guy 2: *fires 2 milisec. before guy 1*
guy 1: "Pw...aww dammit, fauxpwned."