When a male with facial hair performs oral sex
on a female who hasn't showered recently, his moustache and beard will pick up the odour of the female's genitalia
. When this happens the male will be carrying a pusstache on his top lip until he's able to wash his face.
Huey: 'I had too many beers the other night and went home with that sweaty girl who works behind the bar.'
Dewey: 'Don't tell me you...'
Huey: 'I must have done, because the next morning I had a pusstache so strong it made the flowers in my kitchen wilt
. and they were plastic!'