Source : Webster's Revised Unabridged Dictionary (1913)

Picnic \Pic"nic\, n. [Cf. F. piquenique. See {Pick}, v., and cf.
   {Knickknack}.]
   Formerly, an entertainment at which each person contributed
   some dish to a common table; now, an excursion or pleasure
   party in which the members partake of a collation or repast
   (usually in the open air, and from food carried by
   themselves).

Picnic \Pic"nic\, v. i. [imp. & p. p. {Picnicked}; p. pr. & vb.
   n. {Picnicking}.]
   To go on a picnic, or pleasure excursion; to eat in public
   fashion.

Source : WordNet®

picnic
     n 1: a day devoted to an outdoor social gathering [syn: {field
          day}, {outing}]
     2: any undertaking that is easy to do; "marketing this product
        will be no picnic" [syn: {cinch}, {breeze}, {snap}, {duck
        soup}, {child's play}, {pushover}, {walkover}, {piece of
        cake}]
     3: any informal meal eaten outside or on an excursion
     [also: {picnicking}, {picnicked}]

picnic
     v : eat alfresco, in the open air; "We picnicked near the lake
         on this gorgeous Sunday"
     [also: {picnicking}, {picnicked}]