Merriam-Webster Collegiate Dictionary - miasma

 noun  (plural -mas; also ~ta)  Etymology: New Latin, from Greek, defilement, from miainein to pollute  Date: 1665  1. a vaporous exhalation formerly believed to cause disease; also a heavy vaporous emanation or atmosphere a ~ of tobacco smoke  2. an influence or atmosphere that tends to deplete or corrupt freed from the ~ of poverty — Sir Arthur Bryant; also an atmosphere that obscures ; fog retreated into an asexual mental ~ — Times Literary Supplement  • ~l adjective  • ~tic adjective  • miasmic adjective  • miasmically adverb