bat

If you are talking about a baseball bat, then just mime making a couple very small swings with a "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:

BAT ANIMATION
(660KB .gif file. Suggestion: After clicking, switch back to main window and browse while waiting for the new secondary window to download the animation.)

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

FLYING:

FLYING ANIMATION
(197 KB .gif file)

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

VAMPIRE:

VAMPIRE ANIMATION
(85KB .gif file)

Sign: bat
Synonyms:
Handshape:
Right Hand:
Left Hand:
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Non-Manual Marker:
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Inflections: