Lewis & Short

văpōrātĭo, ōnis, f. [vaporo], a steaming, reeking, steam, vapor (post-Aug.): inundantium aquarum, Sen. Q. N. 6, 11: urinae impubium, Plin. 28, 6, 18, § 65: balinearum, a steam-bath, vapor-bath, id. 28, 4, 14, § 55.
Esp., a fomentation, Cael. Aur. Acut. 1, 17, 171 al.