One who doesn't fall in any category of people (cliques).

A young White man confused about his culture and ressembles a Black man. He is in between.. he is a Tweener.

In an episodic series (comic book, tv show, etc.), an episode in which nothing significant happens, but that is necessary to bridge the gap between the episodes that come before and after it.

white person who thinks hes black
yet the blacks dont like him because hes white
yet the whites dont like him because he thinks hes black

thus it leaves him as a outcast

The flap of skin between a man's anus and his ballsack,
It is called a Tweener because it is "tween the balls and tween the anus."

When a male has a half way boner. It's not quite hard, but it's not soft anymore.

Kid between the ages of 7 and 12. No longer a "little kid," but not yet a teenager; in-beTWEEN.