'M1' definitions:

Definition of 'M1'

(from WordNet)
noun
A measure of the money supply; includes currency in circulation plus demand deposits or checking account balances

Definition of 'M1'

From: GCIDE
  • M1 \M1\ n. The narrowest measure of the money supply, comprising the currency in circulation plus demand deposits or checking account balances. [WordNet 1.5]