Obs. exc. dial. [var. of FIRST sb.] The ridge of the roof of a house: see quot. 1819.
1703. Moxon, Mech. Exerc., 142. The Fust of the House.
1819. Nicholson, Dict. Archit., Fust, a term used in Devonshire, and perhaps in some other counties, for the ridge of a house.
