a;tomoj
Strong's #0823

1) Moment

1) This word is a hapax legomenon in the NT 
2) It does not appear in the LXX  
3) In the one verse where it appears Paul defines the term two ways:

a) As to its duration he sees that it will last for the period of "the twinkling of an eye."
b) When this particular moment happens will be "at the last trump."

4) From te,mnw (cut) but with an alpha privative.  It is an amount of time that cannot be subdivided.