in geometry, a quadrilateral figure, both equilateral and equiangular. See Geometry.

SQUARE ROOT. See Arithmetic, p. 420.

HOLLOW SQUARE, in the military art, is a body of foot drawn up with an empty space in the middle for the colours, drums, and baggage; faced and covered by the pikes every way, to keep off horse.

an instrument consisting of two rules, or branches, fastened perpendicularly at one end of their extremes, so as to form a right angle: it is of great use in the description and mensuration of right angles, and laying down perpendiculars.