Joist
WordNet
noun
(1) Beam used to support floors or roofs
WiktionaryText
Noun
joist
- 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.