a bottle cap

plural of trencherful

(geometry) a theorem stating that if a set of points P_i lying on a line is isometrically mapped to points P_i' on a different line, then the midpoints of the segments P_iP_i' also lie on a line.

(chemistry, dated) An acid prepared by dissolving mellonuret of potassium in boiling water, and adding hydrochloric acid, sulphuric acid, or nitric acid.