Green’s Dictionary of Slang

1. (US black) a window.

1944		‘Jiver’s Bible’ in D. Burley Orig. Hbk of Harlem Jive.
1994		C. Major Juba to Jive.

2. (US Und.) a federal narcotics agent.

1931		G. Milburn ‘Convicts’ Jargon’ in AS VI:6 438: gazer, n. A government narcotic agent.
1949		Monteleone Criminal Sl. (rev. edn).
1959		Murtagh & Harris Who Live In Shadow (1960) 17: He is one man sure to attract all the gazers, all the whiskers and uncles, all the narcotics agents.

3. (US black) a mirror.

1943

D. Burley N.Y. Amsterdam News 18 Sept. 22: When you look into your gazer you’ll be sharp just like a razor.