The Collaborative International Dictionary of English v.0.48:

Stew \Stew\, v. t. [imp. & p. p. Stewed; p. pr. & vb. n.
   Stewing.] [OE. stuven, OF. estuver, F. ['e]tuver, fr. OF.
   estuve, F. ['e]tuve, a sweating house, a room heated for a
   bath; probably of Teutonic origin, and akin to E. stove. See
   Stove, and cf. Stive to stew.]
   To boil slowly, or with the simmering or moderate heat; to
   seethe; to cook in a little liquid, over a gentle fire,
   without boiling; as, to stew meat; to stew oysters; to stew
   apples.
   [1913 Webster]

WordNet (r) 3.0 (2006):

stewing
    n 1: an extreme state of worry and agitation; "his stewing over
         the fight kept him awake most of the night"
    2: cooking in a liquid that has been brought to a boil [syn:
       boiling, stewing, simmering]