Geom. [f. Gr. στερεός solid + RADIAN sb.] A unit of measurement of solid angles (see quot. 1881).
1881. Halsted, Mensuration, 78. A steradian is the angle subtended at the center by that part of every sphere equal to the square of the radius.
1883. W. Thomson, in Encycl. Brit., XVI. 25/2. Number of Steradians in an Angle.
1885. A. Macfarlane, Phys. Arith., 87. The unit-rate S per (L. radius)2 is sometimes called a steradian, that is, a solid radian.
