M1

Noun

 * 1)  The amount of cash in circulation plus the amount in bank accounts.
 * 2)  The number two, as the first Mersenne prime.
 * 3)  A system on a chip designed by Apple which was introduced in 2020.
 * 4)  A motorway number; notably the  in England.
 * 5)  A semi-automatic rifle that was the service rifle of the U.S. Army during World War II and the Korean War.