The Collaborative International Dictionary of English v.0.48:

Eructation \Er`uc*ta"tion\, n. [L. eructatio: cf. F.
   ['e]ructation.]
   1. The act of belching wind from the stomach; a belch.
      [1913 Webster]

   2. A violent belching out or emitting, as of gaseous or other
      matter from the crater of a volcano, geyser, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

eructation
    n 1: (of volcanos) pouring out fumes or lava (or a deposit so
         formed) [syn: eruption, eructation, extravasation]
    2: a reflex that expels gas noisily from the stomach through the
       mouth [syn: belch, belching, burp, burping,
       eructation]