\Ca*tad"ro*mous\, a. [Gr. kata` down + dro`mos a
running.]
1. (Bot.) Having the lowest inferior segment of a pinna
   nearer the rachis than the lowest superior one; -- said of
   a mode of branching in ferns, and opposed to {anadromous}.
2. (Zo["o]l.) Living in fresh water, and going to the sea to
   spawn; -- opposed to {anadromous}, and said of the eel.