The Collaborative International Dictionary of English v.0.48:

phosphine \phos"phine\ (f[o^]s"f[=e]n or f[o^]s"f[i^]n), 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]

   Note: 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]

The Collaborative International Dictionary of English v.0.48:

Phosphine \Phos"phine\, n. (Dyeing)
   Chrysaniline, often in the form of a salt.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

phosphine
    n 1: a colorless gas with a strong fishy smell; used as a
         pesticide