well "snum" comes from a mix of snot and cum , and heres the def. : It can happen two ways. #1:After a female or male give a guy a long blowjob ,and he shots his wad in her/his mouth and a few seconds after that before she/he swallows she/he sneezes resulting in the snot and cum to mix and come out her nose . #2:When you sneeze at the exact second you orgasm , feels very strange and cool.
dude 1 "Man after a long bj this chick took down my load and then she sneezed and it landed on my chest , it was gnarly dude"
dude 2 "Man awesome , when I was jackin off I sneezed right when I was about to shot my jizm all over , it awesome dude."