Source : Webster's Revised Unabridged Dictionary (1913)

Gratuitous \Gra*tu"i*tous\a. [L. gratuitus, from gratus
   pleasing. See {Grate}, a., {Gratis.}]
   1. Given without an equivalent or recompense; conferred
      without valuable consideration; granted without pay, or
      without claim or merit; not required by justice.

            We mistake the gratuitous blessings of Heaven for
            the fruits of our own industry.       --L'Estrange.

   2. Not called for by the circumstances; without reason,
      cause, or proof; adopted or asserted without any good
      ground; as, a gratuitous assumption.

            Acts of gratuitous self-humiliation.  --De Quincye.
      -- {Gra*tu"i*tous*ly}, adv. -- {Gra*tu"i*tous*ness}, n.

Source : WordNet®

gratuitous
     adj 1: without cause; "a gratuitous insult"
     2: costing nothing; "complimentary tickets" [syn: {complimentary},
         {costless}, {free}, {gratis(p)}]
     3: unnecessary and unwarranted; "a strikers' tent camp...was
        burned with needless loss of life" [syn: {needless}, {uncalled-for}]