The Collaborative International Dictionary of English v.0.48:
curtainless \curtainless\ adj. not provided with curtains; as, blank, curtainless windows stared back at her. Opposite of curtained. Syn: uncurtained. [WordNet 1.5]WordNet (r) 3.0 (2006):
curtainless adj 1: not provided with curtains; "blank, curtainless windows stared back at her" [syn: curtainless, uncurtained] [ant: curtained]