Green’s Dictionary of Slang

(US) a drive-in cinema.

1948		Time 26 Apr. 96/2: This week New York City will get it’s first ‘ozoner’: a 600-car, $300,000 affair on Staten Island.
1952		N.Y. Times 9 March X 2/7: In the movie trade, drive-ins – or ozoners, as Variety calls them – are ‘passion pits with pix’.