\Tan*gen"tial\, a. (Geom.)
Of or pertaining to a tangent; in the direction of a tangent.
{Tangential force} (Mech.), a force which acts on a moving
   body in the direction of a tangent to the path of the
   body, its effect being to increase or diminish the
   velocity; -- distinguished from a normal force, which acts
   at right angles to the tangent and changes the direction
   of the motion without changing the velocity.
{Tangential stress}. (Engin.) See {Shear}, n., 3.