What does "lumber" mean?

Additional senses

1. 2.Timber sawed or split into the form of beams, joists, boards, planks, staves, hoops, etc.; esp., that which is smaller than heavy timber. [U.S.] Lumber kiln, a room in which timber or lumber is dried by artificial heat. [U.S.] -- Lumber room, a room in which unused furniture or other lumber is kept. [U.S.] -- Lumber wagon, a heavy rough wagon, without springs, used for general farmwork, etc.
2. 3.To heap together in disorder. " Stuff lumbered together." Rymer.
3. 4.To fill or encumber with lumber; as, to lumber up a room.
4. 5.To move heavily, as if burdened.
5. 6.Etym: [Cf. dial. Sw. lomra to resound.] To make a sound as if moving heavily or clumsily; to rumble. Cowper.
6. 7.To cut logs in the forest, or prepare timber for market. [U.S.]