Green’s Dictionary of Slang

ab n.1

[abbr.]

1. [19C+] (Aus.) an Aboriginal; the predecessor of the modern abo n. (1)

2. [mid-19C] (US) an Abolitionist.

3. [1960s+] an abdominal muscle, usu. in the context of a flat stomach; often in pl.

4. attrib. use of sense 2.

5. [2000s] (Aus.) abalone.