noun
gay cruising spot; gay pick-up joint
Refers to a place where gay men meet for casual sexual encounters, such as a bar, sauna, or outdoor area. The term is specific to gay male subculture.
See also: ホモバー
新宿二丁目にはハッテン場がいくつかある。
There are several cruising spots in Shinjuku Ni-chōme.
彼はハッテン場で知り合った人と付き合い始め
He started dating someone he met at a pick-up joint.
ホモバー is a gay bar, which may or may not function as a cruising spot. ハッテン場 specifically emphasizes the cruising or pick-up aspect.
From 発展 (はってん, 'development') + 場 (ば, 'place'), originally a euphemism for a place where 'developments' (sexual encounters) happen. The katakana spelling ハッテン場 is now standard in this context.