What is Lumber ?
Lumber is (noun) 1. junk, old articles which you are not using at the moment I am going to take some of this useless lumber to the jumble sale. 2. US trees which have been cut down The lumber is tied together in rafts and floated down river to the sawmill. (NOTE: The British term is timber.) (verb) 1. to lumber someone with something to give someone things he or she doesn’t want (informal.) You always manage to lumber me with the worst jobs. Why do I always get lumbered with doing the shopping? 2. to move slowly and heavily The tractor lumbered across the field pulling a trailer full of hay. Watch where you’re treading, you lumbering great hulk! (NOTE: Do not confuse with lumbar.)
source: Easier English, Student Dictionary Upper Intermediate Level