(Sax. thrilan, to perforate; Ger. drilien, to turn, to twist), a tool with a steel point, used for perforating metal, ivory, and other hard substances. It is worked by a moderate pressure, with a whirling motion, which is usually communicated to it either by a drill-box, or by means of a nut made to play on a spiral shaft in the end of which the steel point is fixed. The extremity of the borer is generally somewhat flattened, and of an angular shape, thus , with sharp edges.

in Agriculture, a machine for sowing seeds in regular rows. See Agriculture, vol. ii. p. 274.