from The American Heritage® Dictionary of the English Language, 5th Edition.

  • adjective Of, relating to, or located on the part of a radially symmetric animal from which the tentacles radiate or the side where the oral area is found.

from The Century Dictionary.

  • In zoology: Pertaining to the side of a radiate animal which contains the mouth: equivalent to oral, since the pole, surface, or aspect of the body whence parts radiate is also that in which the mouth is situated: the opposite of abactinal or aboral.
  • In general, having tentacles or rays.

from the GNU version of the Collaborative International Dictionary of English.

  • adjective (Zoöl.) Pertaining to the part of a radiate animal which contains the mouth.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • adjective zoology Pertaining to the side or surface around the mouth in an animal that has radial symmetry such as a starfish.
  • adjective zoology Pertaining to the axis of rotational symmetry in radiate animals.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adjective (of radiate organisms) located on the surface or end on which the mouth is situated


from Wiktionary, Creative Commons Attribution/Share-Alike License

From Ancient Greek ἀκτίς, ἀκτῖν- (actis, actin-, "ray") +‎ -al. The usage was coined by Louis Agassiz (See quotations below.).


  • [Footnote: When reference is made to the whole structure, including the internal organs as well as the solid parts of the surface, the terms _actinal_ and _ab-actinal_ are preferable to oral and ab-oral.] [Illustration: Sea-Urchin seen from the oral side, showing the zones with the spines and suckers; for the ab-oral side, on the summit of which the zones unite, see February Number, p. 216.]

    The Atlantic Monthly, Volume 10, No. 57, July, 1862


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