The Collaborative International Dictionary of English v.0.48:

Ganancial \Ga*nan"cial\, a. [Sp., pertaining to gain, held in
   common, fr. ganancia gain.] (Law)
   Designating, pertaining to, or held under, the Spanish system
   of law (called

   ganancial system) which controls the title and disposition
      of the property acquired during marriage by the husband or
      wife.
      [Webster 1913 Suppl.]