The Collaborative International Dictionary of English v.0.48:
Unhallow \Un*hal"low\, v. t. [1st pref. un- + hallow.] To profane; to desecrate. [1913 Webster] The vanity unhallows the virtue. --L'Estrange. [1913 Webster]WordNet (r) 3.0 (2006):
unhallow v 1: remove the consecration from a person or an object [syn: desecrate, unhallow, deconsecrate] [ant: bless, consecrate, hallow, sanctify]