Green’s Dictionary of Slang

1. (Irish) terrible, shocking, unpleasant, rough.

1993		(con. 1930s) M. Verdon Shawlies, Echo Boys, the Marsh and the Lanes 151: ’Twas a terrible time, really and truly. The poverty was cat.
2004		P. Howard PS, I Scored the Bridesmaids 203: This Cork bird [...] who’s basically cat, roysh, though not bad for an ugly focker like him.

2. (US campus) likeable, approved of [on the bad = good model].

1983

Eble Campus Sl. Mar. 1: cat – acceptable to the in group: I invited her to the party because she was cat.