Source : Webster's Revised Unabridged Dictionary (1913)

Basking shark \Bask"ing shark`\ (Zo["o]l.)
   One of the largest species of sharks ({Cetorhinus maximus}),
   so called from its habit of basking in the sun; the liver
   shark, or bone shark. It inhabits the northern seas of Europe
   and America, and grows to a length of more than forty feet.
   It is a harmless species.

Source : WordNet®

basking shark
     n : large harmless plankton-eating northern shark; often swims
         slowly or floats at the sea surface [syn: {Cetorhinus
         maximus}]