The Collaborative International Dictionary of English v.0.48:

Cartilaginous \Car`ti*lag"i*nous\, a. [L. cartilaginosus: cf. F.
   cartilagineux.]
   1. Of or pertaining to cartilage; gristly; firm and tough
      like cartilage.
      [1913 Webster]

   2. (Zool.) Having the skeleton in the state of cartilage, the
      bones containing little or no calcareous matter; said of
      certain fishes, as the sturgeon and the sharks.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cartilaginous
    adj 1: of or relating to cartilage
    2: difficult to chew [syn: cartilaginous, gristly,
       rubbery]