• (a.) Pertaining to the surface or end opposite to the mouth in a radiate animal; -- opposed to actinal.
<zoology> Pertaining to the surface or end opposite to the mouth in a radiate animal; opposed to actinal. The aboral or abactinal area. ... Origin: L. Ab + E. Actinal. ... (19 Mar 1998) ... 
Ab·ac'ti·nal (ăb*ăk'tĭ*n a l) adjective [ Latin ab + English actinal .] (Zoology) Pertaining to the surface or end opposite to the mouth in a radiate animal; -- opposed to actinal . 'The aboral or abactinal area.' Latin Agassiz. 
In zoology, abactinal refers to the surface or end opposite to the mouth in a radiate animal.
[adj] - (of radiate animals) located on the surface or end opposite to that on which the mouth is situated
adjective (of radiate animals) located on the surface or end opposite to that on which the mouth is situated