ABACTINAL
abactinal
(adjective) (of radiate animals) located on the surface or end opposite to that on which the mouth is situated
Source: WordNet® 3.1
Etymology
Adjective
abactinal (comparative more abactinal, superlative most abactinal)
(zoology) Pertaining to the surface or end opposite to the mouth in a radiate animal.
Antonym: actinal
Source: Wiktionary
Ab*ac"ti*nal, a. Etym: [L. ab + E. actinal.] (Zoöl.)
Definition: Pertaining to the surface or end opposite to the mouth in a
radiate animal; -- opposed to actinal. "The aboral or abactinal
area." L. Agassiz.
Source: Webster’s Unabridged Dictionary 1913 Edition