Literally refers to young children, who often have colds but don't wipe their nose. Commonly used as a derogatory term to describe someone who is childish in behavior or appearance.
These snot-nosed kids tried to get into this club with their fake IDs, but the bouncer threw them out.
by Evil Timmy November 18, 2003
At the checkout line, a snot nosed soccer mom asked to cut in line because she had to pick up her brat at day care. I told her to bugger off.
by Tuna Wanda May 24, 2005