Source : Webster's Revised Unabridged Dictionary (1913)

Munch \Munch\, v. t. & i. [imp. & p. p. {Munched}; p. pr. & vb.
   n. {Munching}.] [Prob. akin to mumble: cf. also F. manger to
   eat (cf. {Mange}), and m[^a]cher to cher (cf. {Masticate}).
   See {Mumble}.]
   To chew with a grinding, crunching sound, as a beast chews
   provender; to chew deliberately or in large mouthfuls.
   [Formerly written also {maunch} and {mounch}.]

         I could munch your good dry oats.        --Shak.