1.A goat is a underage girl, usually a slut. It comes from common sense, You wouldn't have sex with a goat, so why would you have sex with a underage chick?
A fag. Someone who butt rams gay men. Word decends from full term Fagoot, which is same as fagot pronouced diferently. This later got shortened to goat to desguise rippingpeople.
When someone in a large group, most likely at a party, drinks or smokes to much ganja and freaks out. Either starts tripping out unnecessarily, throwing up, crying, or a mixture of all.
"Where is Billie? "
"Oh she is goating out in the bathroom. "
"Yeah, she turns into a real goat when she smokes."