Indivisible

n.
  1. That which is indivisible.
  2. (Geom.) An infinitely small quantity which is assumed to admit of no further division.
    3. 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.