Wordnet 3.0
NOUN (1)
1.
photographic equipment used to synchronize sound and motion picture;
boards held in front of a movie camera are banged together;
The Collaborative International Dictionary of English v.0.48:
clapperboard \clap"per*board`\ (kl[a^]p"p[~e]r*b[=o]rd`), n.
a device which synchronizes sound and picture while making a
motion picture, consisting of boards held in front of a movie
camera, which are are banged together.
[WordNet 1.5]
WordNet (r) 3.0 (2006):
clapperboard
n 1: photographic equipment used to synchronize sound and motion
picture; boards held in front of a movie camera are banged
together