Green’s Dictionary of Slang

phat adj.

[deliberately skewed sp. of fat adj. (1c); but also popularly linked to a variety of suggested acronyms, e.g. physically attractive or pretty hips and thighs or pretty hips, ass and tits, or pretty hot and tempting, or pussy, hips, ass and thighs etc.]

1. [1960s+] (orig. US black/campus) used to describe an attractive woman.

2. [1990s+] (also phat-ass, phatman sweet) a general term of approval, admiration; also in phrs., e.g. phat 2 death.

In compounds

phat-cat (n.)

[1990s+] (US campus) a very fashionable person.

phat pocket (n.)

[1990s+] (US black) a wealthy person; also attrib.

phat tape (n.) (also fat tape)

[1990s+] (US black teen) an exceptionally good mix tape.