The Collaborative International Dictionary of English v.0.48:

Madrepore \Mad"re*pore\, n. [F. madrepore, perh. fr. madr['e]
   spotted, fr. OF. madre, mazre, a kind of knotty wood with
   brown spots, fr. OHG. masar a knot, grain, or vein in wood, a
   speck, G. maser + pore (see Pore); or perh. F. madr['e]pore
   is rather from It. madrepora, and this perh. fr. It. madre
   mother (see Mother) + Gr. ? a soft stone.] (Zool.)
   Any coral of the genus Madrepora, a group of corals having
   calcareous skeletons aggregations of which form reefs and
   islands; formerly, often applied to any stony coral.

   Syn: stony coral, madriporian coral.
        [1913 Webster]

WordNet (r) 3.0 (2006):

madrepore
    n 1: corals having calcareous skeletons aggregations of which
         form reefs and islands [syn: stony coral, madrepore,
         madriporian coral]