Green’s Dictionary of Slang

hot pillow n.

(US) a casual, short-time sexual encounter; usu. attrib., in combs., e.g. hot-pillow motel (cf. hot-sheet adj.).

Collans & Sterling I Was a House Detective 219: Hot-pillow House. Cheap hotel which rents a room several times a night .
W.J. Coughlin Stalking Man 114: We’ll find a little hot-pillow joint and fool around.
[US]R. Campbell In La-La Land We Trust (1999) 128: ‘There a hotel or motel close by?’ [...] ‘The Blue House is right next door to the Beaver Run [...] Special rate. Ten bucks for a hot pillow’. [Ibid.] 132: Having a one off in some hot pillow joint along the boulevard where fifty bucks bought the works.
R.W. Campbell Juice 310: What’s he doing in a hot-pillow motel in Studio City, the money he’s got.
J.R. Garber Vertical Run 75: New York landlords use their second floors for temporary space, renting offices like rooms in a hot pillow motel.
A.F. Wood Road Trip America 58: The most famous ‘hot pillow’ joint ever built. The Coral Court Motel, located on the outskirts of St. Louis.
J.C. Baldwin Suddenly No Warning 70: The desk clerk at the motel [...] remembered Claire and Marshall, routine hot-pillow customers.
L. Block Community of Women (Internet edn) n.p.: Otis Wheeler was a voyeur, and there is no place for a voyeur quite so delightful as a hot-pillow joint.
R.F. Kennedy Day Watch at Hollywood 63: They found him at a Hollywood hot pillow motel in the company of a fake blonde named Nikki Raye.

In compounds

hot-pillow trade (n.)

the sex industry, spec. casual prostitution.

H.A. Smith Two-thirds of a Coconut Tree 289: The big tourist hotels are not to engage in the hot-pillow trade any longer.
O.D. Richardson Phantom Homestead 47: A certain number made a good living out of what is called the ‘hot pillow’ trade.
K.T. Jackson Crabgrass Frontier 254: Many of Hoover’s ‘dens of vice’ were once decent places that, unable to keep up, turned to the ‘hot pillow trade.’.
T. Wood Dead in the Water 26: It specialized in the hot pillow trade, except in midsummer when genuine moms and pops kept the rooms full.
B. McKercher Sex and Tourism 88: The casual in-room sex industry has become known as the ‘hot pillow’ trade.
W. Kibicho Sex Tourism in Africa 93: In Kenya, this casual in-room sexual service is called pillow moto, or ‘hot-pillow trade’.