Phosphine

n. (Chem.) A colorless gas, PH3, analogous to ammonia, and having a disagreeable odor resembling that of garlic. Called also hydrogen phosphide, and formerly, phosphureted hydrogen. It is postulated as one possible cause of the rare lights seen in marshes -- see ignis fatuus. [ 1913 Webster + PJC ]

☞ It is the most important compound of phosphorus and hydrogen, and is produced by the action of caustic potash on phosphorus. It is spontaneously inflammable, owing to impurities, and in burning produces peculiar vortical rings of smoke. [ 1913 Webster ]