One who acts like a complete jackass in order to seem cool. When someone acts like a "bat" they are ussualy under the influence of weed or alcohol or maybe even both in some cases. People who act like bats are also refered to as "That Guy", or more generally a "JP".
Bryan smokes alot of pot, then drinks alot, he then proceeds to "fly" around the room as a bat acting like a complete idiot. When he stops, someone then tells him, nigga, you a bat right now.
by ThatloserGuy January 26, 2008