The Collaborative International Dictionary of English v.0.48:

Gumption \Gump"tion\, n. [OE. gom, gome, attention; akin to AS.
   ge['o]mian, gyman, to regard, observe, gyme care, OS. gomean
   to heed, Goth. gaumjan to see, notice.]
   [1913 Webster]
   1. Capacity; shrewdness; common sense. [Colloq.]
      [1913 Webster]

            One does not have gumption till one has been
            properly cheated.                     --Lord Lytton.
      [1913 Webster]

   2. (Paint.)
      (a) The art of preparing colors. --Sir W. Scott.
      (b) Megilp. --Fairholt.

   3. initiative; resourcefulness.
      [PJC]

   4. Courage; guts.
      [PJC]

WordNet (r) 3.0 (2006):

gumption
    n 1: sound practical judgment; "Common sense is not so common";
         "he hasn't got the sense God gave little green apples";
         "fortunately she had the good sense to run away" [syn:
         common sense, good sense, gumption, horse sense,
         sense, mother wit]
    2: fortitude and determination; "he didn't have the guts to try
       it" [syn: backbone, grit, guts, moxie, sand,
       gumption]