Definition of joist :
1. A piece of timber laid horizontally, or nearly so, to which the planks of the floor, or the laths or furring strips of a ceiling, are nailed; -- called, according to its position or use, binding joist, bridging joist, ceiling joist, trimming joist, etc. See Illust. of Double- framed floor, under Double, a.
2. To fit or furnish with joists.
beam (part of speech: noun)
- Near the uprights was an extra piece of joist standing on end as if forming a portion of the side. - "Down the Slope", James Otis.
- You may drag them off; but the first one who dares so much as raise a joist for any other purpose, shall suffer! - "Down the Slope", James Otis.
- A dull thud told of the trap fully raised and resting upon some supporting joist. - "The Devil Doctor", Sax Rohmer.