adj. & n.
--adj.
1. implacably hostile.
2 (of ideas etc.) incompatible.
--n.
1. an uncompromising opponent of a political measure etc.
2 (usu. in pl.) any of two or more items, ideas, etc., that cannot be made to agree.
Derivatives:
irreconcilability n. irreconcilableness n. irreconcilably adv.