The Collaborative International Dictionary of English v.0.48:
Fornicate \For"ni*cate\, Fornicated \For"ni*ca`ted\, a. [L. fornicatus, fr. fornix, -icis, an arch, vault.] 1. Vaulted like an oven or furnace; arched. [1913 Webster] 2. (Bot.) Arching over; overarched. --Gray. [1913 Webster]