From Late Latin posse (“to be able (to have)”) comitatus (“a company”).
posse comitatus (uncountable)
- (historical) The able-bodied men over 15 in a given county who can be summoned by the sheriff to help keep the peace, or arrest a felon; also a group of men so gathered.
- 1849, Henry David Thoreau, Resistance to Civil Government:
- They are the standing army, and the militia, jailers, constables, posse comitatus, etc.
- (figuratively) Any band of men, especially armed or hostile.
- 1819, Lord Byron, Don Juan, I:
- With him retired his ‘posse comitatus,’ / The attorney last, who linger'd near the door / Reluctantly [...].