Source : Webster's Revised Unabridged Dictionary (1913)

Lunch \Lunch\, n. [Of uncertain etymol. Cf. Prov. Eng. nunc a
   lump.]
   A luncheon; specifically, a light repast between breakfast
   and dinner.

Lunch \Lunch\, v. i. [imp. & p. p. {Lunched}; p. pr. & vb. n.
   {Lunching}.]
   To take luncheon. --Smart.

Source : WordNet®

lunch
     n : a midday meal [syn: {luncheon}, {tiffin}, {dejeuner}]

lunch
     v 1: take the midday meal; "At what time are you lunching?"
     2: provide a midday meal for; "She lunched us well"