lobo, n. — Green’s Dictionary of Slang

lobo n.

[SE lobo, a grey wolf]

1. (US black) an unattractive woman [synon. for dog n.² (8)].

1942		Pittsburgh Courier (PA) 22 Aug. 7/5: Lobo — (ugly girl).
1947		M.H. Boulware Jive and Sl.

2. (US) an outsider, a loner.

1947–53

W. Guthrie Seeds of Man (1995) 224: If that old lobo alligator, Old Man Rio, asks me where I’ve been [...] I’m gonna tell him.