The Collaborative International Dictionary of English v.0.48:

mahimahi \mahimahi\ n.
   1. either of two large slender food and game fish
      (Coryphaena equisetis or Coryphaena hippurus) of warm
      waters. They are highly esteemed as food fish, especially
      in Hawaii. See also dolphin[2].

   Syn: dolphin, dolphinfish.
        [WordNet 1.5 +PJC]

   2. lean-fleshed fish of warm waters, esp. Hawaii.

   Syn: dolphinfish.
        [WordNet 1.5] mahjong

The Collaborative International Dictionary of English v.0.48:

dolphinfish \dolphinfish\ n.
   either of two large slender food and game fish (Coryphaena
   equisetis or Coryphaena hippurus) of warm waters. They are
   highly esteemed as food fish, especially in Hawaii, where
   they are usually referred to as mahimahi. See also
   dolphin[2].

   Syn: dolphin, mahimahi.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

Coryphaena hippurus
    n 1: the more common dolphinfish valued as food; about six feet
         long