a. Zool. [f. L. ab away from + ACTINAL.] Remote from the actinal area; pertaining to that part of the surface of a radiated animal which is opposite to the mouth, e.g., the apex of a sea-urchin, or upper surface of a star-fish. See ACTINAL.
1857. L. Agassiz, Contrib. Nat. Hist. America, IV. 376. I have called this side … the oral or actinal area, and the opposite side the aboral or abactinal area.
1864. A. Agassiz, in Reader, No. 85, 204/2. The spines on the abactinal area.
1881. Mackintosh, in Nature, No. 628, 41. The abactinal system and ambulacral plates of a Cidarid combined with the thin test and hollow spines of a Diadema.
