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1.
Horny; dealing with all thoughts of sex and its fantastic acts.
"I was so sinful last night that I almost had to change my panties," my friend Jackie would say.
by foxxylady May 14, 2006
 
2.
doing naughty things, being bad, doing something that society sees as bad or wrong, being evil, not caring, comiting a sin.
example 1:
person 1: Hey did u comit a sin last night?
person 2: Yes, i had a one night stand, if that's what you ment.

example 2:

I didn't listen to my parents. Oh, i'm so sinful.

example 3:
I like that hot ass guy with tattoos! He looks so sinful.
by daymgirl January 06, 2010