Minutemen were members of the organized New England colonial militia companies during the American Revolutionary War (1775-1783). They got the name from the fact they were expected to be ready for battle at a minute’s notice.
In the Massachusetts Bay colony, all able-bodied men between the ages of 16 and 60 were required to participate in the local militia. This is the type of militia the founders had in mind when they drafted the Second Amendment to the Constitution:
A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.