The Collaborative International Dictionary of English v.0.48:

Arsine \Ar"sine\ ([aum]r"s[i^]n or -s[=e]n), n. [From
   Arsenic.] (Chem.)
   A compound of arsenic and hydrogen, AsH3, a colorless and
   exceedingly poisonous gas, having an odor like garlic;
   arseniureted hydrogen.
   [1913 Webster]

WordNet (r) 3.0 (2006):

arsine
    n 1: a poisonous colorless flammable gas used in organic
         synthesis and to dope transistors and as a poison gas in
         warfare