The Collaborative International Dictionary of English v.0.48:
Headboard \Head"board`\ (h[e^]d"b[=o]rd`), n. A board or boarding which marks or forms the head of anything; as, the headboard of a bed; the headboard of a grave. HeadboroughWordNet (r) 3.0 (2006):
headboard n 1: a vertical board or panel forming the head of a bedstead