Definition of mousetail in US English:



  • 1The tail of a mouse.

  • 2A dwarf plant of seasonally wet places, Myosurus minimus (family Ranunculaceae), with single tiny yellowish-green flowers and numerous achenes in an elongating spike, which is native to Old World temperate regions and naturalized elsewhere. Also (with distinguishing word): any of several related North American species of Myosurus.

  • 3In full "mousetail grass". A foxtail grass with a slender spike, especially black grass, Alopecurus myosuroides. Also (British regional) in plural with singular concord. Now rare.

  • 4A fescue grass of the genus Vulpia having a narrow panicle; specifically (more fully "mousetail fescue" (also "mousetail fescue-grass"), †"mousetail grass"), rat's-tail fescue, V. myuros.

  • 5In singular and plural US slang. A moustache; specifically a pencil-line moustache. Now rare.


Late Middle English; earliest use found in Guy de Chauliac's Grande Chirurgie. From mouse + tail.