Green’s Dictionary of Slang

yapper n.

1. (Aus.) a racing greyhound.

[Aus]J. Byrell Lairs, Urgers & Coat-Tuggers 334: it’s also not a bad idea to avoid the 3, 4 and 5 ‘squeeze’ boxes since those yappers tend to get ‘squeezed out’ by the dogs underneath them .

2. see yap n.1 (1a)

3. see yap n.1 (1d)

4. see yap n.1 (1e)