The Collaborative International Dictionary of English v.0.48:

Gratuity \Gra*tu"i*ty\, n.; pl. Gratuities. [F. gratuit['e],
   or LL. gratuitas.]
   1. Something given freely or without recompense; a free gift;
      a present. --Swift.
      [1913 Webster]

   2. Something voluntarily given in return for a favor or
      service, as a recompense or acknowledgment.
      [1913 Webster]