Definition of actinal in English:

actinal

adjective

Zoology
  • Designating the part or surface of an echinoderm or other radiate animal which contains the mouth and surrounding organs (as the lower or oral side of a starfish); relating to this part.

    Originally introduced in connection with Agassiz's theory that the body of a radiate animal is essentially a sphere, with the mouth or actinostome at one of the poles.

Pronunciation

actinal

/akˈtʌɪnl/ /ˈaktɪnl/

Origin

Mid 19th century; earliest use found in Louis Agassiz (1807–1873), zoologist and geologist. From ancient Greek ἀκτῖν-, ἀκτίς ray + -al.