Joist n. Arch. 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.
Trim·ming a. from Trim, v.
The Whigs are, essentially, an inefficient, trimming, halfway sort of a party. --Jeffrey.
Trimming joist Arch., a joist into which timber trimmers are framed; a header. See Header.