The Collaborative International Dictionary of English v.0.48:
Mopboard \Mop"board`\, n. (Carp.) A narrow board nailed against the wall of a room next to the floor; skirting board; baseboard. See Baseboard. [1913 Webster]WordNet (r) 3.0 (2006):
mopboard n 1: a molding covering the joint formed by a wall and the floor [syn: baseboard, mopboard, skirting board]