Green’s Dictionary of Slang

(orig. US) an inquisitive neighbour, usu. a woman.

1859		Bartlett Dict. Americanisms (2nd edn) 448: Stare-Cat, a woman or girl who amuses herself with gazing at her neighbours. A woman’s word .
1877		Union Leader (Wilkes-Barre, PA) 6 Sept. 1/3: The ‘stare-cat’ suad is what they call the old women who sit together [...] for the sole purpose of satring [at] and criticizing new arrivals.
1878		Eve. Star (Wash., DC) 19 July 3/7: ‘Stare-Cats’ — The ‘stare-cat’ squad is what they call the young dandies who stand together on the beach for the sole purpose of staring at and criticising ladies.
1910		Pittsburg Press (PA) 3 Apr. 61/2: A long-seated trolley-car [...] not in the least a discourager to the stare-cat.