The Collaborative International Dictionary of English v.0.48:

M3 \M3\ n.
   A broad measure of the money supply, comprising M2 plus
   deposits at nonbanks such as savings and loan associations.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

M3
    n 1: a measure of the money supply; M2 plus deposits at
         institutions that are not banks (such as savings and loan
         associations)

The Free On-line Dictionary of Computing (30 December 2018):

M3

   A macro processor, forerunner of M4, for the AP-3
   minicomputer.