tertiary action


Also found in: Dictionary, Thesaurus, Legal, Financial, Encyclopedia.
Related to tertiary action: Tertiary education

action, tertiary 

Term referring to the least effect of an extrocular muscle. The tertiary action of the inferior rectus is extorsion; of the superior rectus, intorsion; of the inferior and superior oblique, abduction. The medial and lateral recti muscles are regarded as having only a primary action, at least in the primary position.