The Collaborative International Dictionary
Diriment impediment
Diriment \Dir"i*ment\, a. [L. dirimens, p. pr. of dirimere. See Dirempt.] (Law) Absolute.
Diriment impediment (R. C. Ch.), an impediment that nullifies marriage.
Wiktionary
diriment impediment
n. (context Roman Catholic English) An impediment that nullify marriage.