Source : Webster's Revised Unabridged Dictionary (1913)

Tangential \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.

Source : WordNet®

tangential
     adj 1: of superficial relevance if any; "a digressive allusion to
            the day of the week"; "a tangential remark" [syn: {digressive}]
     2: of or relating to or acting along or in the direction of a
        tangent; "tangential forces"