'Infinitesimal' definitions:

Definition of 'infinitesimal'

From: WordNet
adjective
Infinitely or immeasurably small; "two minute whiplike threads of protoplasm"; "reduced to a microscopic scale" [syn: infinitesimal, minute]
noun
(mathematics) a variable that has zero as its limit

Definition of 'Infinitesimal'

From: GCIDE
  • Infinitesimal \In`fin*i*tes"i*mal\, a. [Cf. F. infinit['e]simal, fr. infinit['e]sime infinitely small, fr. L. infinitus. See Infinite, a.] Infinitely or indefinitely small; less than any assignable quantity or value; very small. [1913 Webster]
  • Infinitesimal calculus, the different and the integral calculus, when developed according to the method used by Leibnitz, who regarded the increments given to variables as infinitesimal. [1913 Webster]

Definition of 'Infinitesimal'

From: GCIDE
  • Infinitesimal \In`fin*i*tes"i*mal\, n. (Math.) An infinitely small quantity; that which is less than any assignable quantity. [1913 Webster]