see also: f.u.s., V-FUS
Common at drinking parties. Can be good or bad.
BAD fus: spilling beer/liquor onto someone (see party foul), people making out with other people's girlfriends, packing heat to a party, pulling knifes/guns on people, lighting things on fire that don't belong to you, high male/female ratio (see sausage fest), or a large ammount of gay guys.
you and your lover were making out. a few school children walk by. you stop back up and pretend to be checking you cell phone. they walk by knowing exactly what was up. this is a F.U.S. moment.