Source : Webster's Revised Unabridged Dictionary (1913)

Interambulacrum \In`ter*am`bu*la"crum\, n.; pl. L.
   {Interambulacra}, E. {Interambulacrums}. (Zo["o]l.)
   In echinoderms, one of the areas or zones intervening between
   two ambulacra. See Illust. of {Ambulacrum}.