Source : Webster's Revised Unabridged Dictionary (1913)

Metonymy \Me*ton"y*my\ (?; 277), n. [L. metonymia, Gr. ?; ?,
   indicating change + ?, for ? a name: cf. F. m['e]tonymie. See
   {Name}.] (Rhet.)
   A trope in which one word is put for another that suggests
   it; as, we say, a man keeps a good table instead of good
   provisions; we read Virgil, that is, his poems; a man has a
   warm heart, that is, warm affections.

Source : WordNet®

metonymy
     n : substituting the name of an attribute or feature for the
         name of the thing itself (as in `they counted heads')