Source : Webster's Revised Unabridged Dictionary (1913)

Baseboard \Base"board\, n. (Arch.)
   A board, or other woodwork, carried round the walls of a room
   and touching the floor, to form a base and protect the
   plastering; -- also called washboard (in England), mopboard,
   and scrubboard.

Source : WordNet®

baseboard
     n : a molding covering the joint formed by a wall and the floor
         [syn: {mopboard}, {skirting board}]