The Collaborative International Dictionary of English v.0.48:

Urethane \U*reth"ane\, n. [F. ur['e]thane. See Urea; Ether.]
   1. (Org. Chem.) A white crystalline substance,
      NH2.CO.OC2H5, produced by the action of ammonia on ethyl
      carbonate or by heating urea nitrate and ethyl alcohol. It
      is used as a hypnotic, antipyretic, and antispasmodic.
      Hence, any ester of carbamic acid.
      [Webster 1913 Suppl.]

   2. same as polyurethane.
      [PJC]

WordNet (r) 3.0 (2006):

urethane
    n 1: an ester of carbamic acid