† coˈarctionObs.rare. [f. coarct v., after act-ion, etc.: see -ion1.] Coarctation, constriction. 1782A. Monro Compar.Anat. (ed. 3) 7 Nor is there any coarction forming the antrum willisii as in the stomach of man.Ibid. 18 These coarctions give way in the time of birth.