dimensional lumber

Lumber Lum"ber, n. [Prob. fr. Lombard, the Lombards being the money lenders and pawnbrokers of the Middle Ages. A lumber room was, according to Trench, originally a Lombard room, or room where the Lombard pawnbroker stored his pledges. See {Lombard}.] 1. A pawnbroker's shop, or room for storing articles put in pawn; hence, a pledge, or pawn. [Obs.] [1913 Webster]

They put all the little plate they had in the lumber, which is pawning it, till the ships came. --Lady Murray. [1913 Webster]

2. Old or refuse household stuff; things cumbrous, or bulky and useless, or of small value. [1913 Webster]

3. 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.] [1913 Webster]

{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.

{dimensional lumber}, lumber, usually of pine, which is sold as beams or planks having a specified nominal cross-section, usually in inches, such a two-by-four, two-by-six, four-by-four, etc. [1913 Webster +PJC]