Search the Dictionary

e indefinitely small angle between two consecutive osculating planes of a curve of double curvature. -- Moment of torsion (Mech.) the moment of a pair of equal and opposite couples which tend to twist a body. -- Torsion balance (Physics.), an instrument for estimating very minute forces, as electric or magnetic attra…

pirally; subjected to torsion; hence, perverted. Twisted curve (Geom.), a curve of double curvature. See Plane curve, under Curve. -- Twisted surface (Geom.), a surface described by a straight line moving according to any law whatever, yet so that the consecutive positions of the line shall not be in one plane; a warp…

A point of a surface at which the curvatures of the normal sections are all equal to each other. A sphere may be osculatory to the surface in every direction at an umbilicus. Called also umbilic.