Joist

n. [O. Fr. giste, N. Fr. gîte, joist; L. Lat. gistum, equivalent to Lat. jacitum, O. Fr. gist, gis (equivalent to Lat. jacitus), p. p. of gésir, Fr. jazer, Lat. jacēre, to lie; Scot. geist, geest, W. dist. joist, beam.] A small piece of timber to which the boards of a floor or the laths of ceiling are nailed. It rests on the wall or on girders. Gwilt.