When a man consumes beer to the extent that he begins to pout, cry, or reminisce upon previous traumatic experiences in his life. Thus forfeiting his manhood, and succumbing to the fact that he now has a vagina.
"After Tommy lost his 6th consecutive game of beer pong, he glanced across the table and noticed his ex-girlfriend making out with his best friend. Tommy then began to cry hysterically until he sat in the corner of the room as all of the girls at the party consoled him. At that point Tommy officially had a beergina."