Source : Webster's Revised Unabridged Dictionary (1913)

Indivisible \In`di*vis"i*ble\, n.
   1. That which is indivisible.

            By atom, nobody will imagine we intend to express a
            perfect indivisible, but only the least sort of
            natural bodies.                       --Digby.

   2. (Geom.) An infinitely small quantity which is assumed to
      admit of no further division.

   {Method of indivisibles}, a kind of calculus, formerly in
      use, in which lines were considered as made up of an
      infinite number of points; surfaces, as made up of an
      infinite number of lines; and volumes, as made up of an
      infinite number of surfaces.