The Collaborative International Dictionary of English v.0.48:

Gestation \Ges*ta"tion\, n. [L. gestatio a bearing, carrying,
   fr. gestare to bear, carry, intens. fr. gerere, gestum, to
   bear: cf. F. gestation. See Gest deed, Jest.]
   [1913 Webster]
   1. The act of wearing (clothes or ornaments). [Obs.]
      [1913 Webster]

   2. The act of carrying young in the womb from conception to
      delivery; pregnancy.
      [1913 Webster]

   3. Exercise in which one is borne or carried, as on
      horseback, or in a carriage, without the exertion of his
      own powers; passive exercise. --Dunglison.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gestation
    n 1: the period during which an embryo develops (about 266 days
         in humans) [syn: gestation, gestation period]
    2: the state of being pregnant; the period from conception to
       birth when a woman carries a developing fetus in her uterus
       [syn: pregnancy, gestation, maternity]
    3: the conception and development of an idea or plan