BAT: The American Sign Language (ASL) sign for "bat"
 

If you are talking about the flying creature that lives in caves (and elsewhere), read on:

The general sign for bat shows how bats like to sleep with their wings folded over their chests while hanging upside down.

BAT:

You can use the sign for "flying" (flapping wings) to represent a bat.

FLYING:

Some people use the sign for "vampire" to mean "bat."  A group of Deaf Teenagers used to sign "VAMPIRE" + "MAN" to mean "Batman."

VAMPIRE:

BATMAN:

If you want to learn more animal signs, check out:

Notes: 

See: ANIMALS