1665, from Gk. miasma (gen. miasmatos) "stain, pollution," related to miainein "to pollute," from PIE base *mei-/*mai- "to stain, defile" (cf. O.E. mal "stain, mark," see mole (1)).
Main Entry: mi·as·ma Pronunciation: mI-'az-m&, mE- Function: noun Inflected Form: pluralmi·as·masalsomi·as·ma·ta/-m&t-&/ : a vaporous exhalation (as of a marshy region or of putrescent matter) formerly believed to cause disease (as malaria) —mi·as·mal/-m&l/adjective —mi·as·mat·ic/"mI-&z-'mat-ik/adjective —mi·as·mic/mI-'az-mik, mE-/adjective