The Collaborative International Dictionary of English v.0.48:
Crossbeam \Cross"beam`\ (-b[=e]m`). n. 1. (Arch.) A girder. [1913 Webster] 2. (Naut.) A beam laid across the bitts, to which the cable is fastened when riding at anchor. [1913 Webster]WordNet (r) 3.0 (2006):
crossbeam n 1: a horizontal beam that extends across something [syn: trave, traverse, crossbeam, crosspiece]