Monoceros \Mo*noc"e*ros\, n. [L., fr. Gr. ?; mo`nos alone, single + ke`ras horn.] 1. A one-horned creature; a unicorn; a sea monster with one horn. [1913 Webster] Mighty monoceroses with immeasured tails. --Spenser. [1913 Webster] 2. (Astron.) The Unicorn, a constellation situated to the east Orion. [1913 Webster]