1. a person, place, or object which has caused annoyance or embarrassment
2. a part of the psychic apparatus that experiences and reacts to the outside world and thus mediates experiences of discomfort, hardship, or embarrassment, most commonly through alcohol
1. to take advantage
Those guys were stains.
I drank fifteen beers last night; my stain is huge right now.
I stained that girl out last night.