The Collaborative International Dictionary of English v.0.48:

Valuable \Val"u*a*ble\, a.
   1. Having value or worth; possessing qualities which are
      useful and esteemed; precious; costly; as, a valuable
      horse; valuable land; a valuable cargo.
      [1913 Webster]

   2. Worthy; estimable; deserving esteem; as, a valuable
      friend; a valuable companion.
      [1913 Webster]

   Valuable consideration (Law), an equivalent or compensation
      having value given for a thing purchased, as money,
      marriage, services, etc. --Blackstone. --Bouvier.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

VALUABLE CONSIDERATION, contracts. An equivalent for a thing purchased. Vide
Vin. Ab. Consideration, B; 2 Bl. Com. 297; Consideration.