(formerly) a mounted marine or cavalryman serving in a ship
2.
someone out of his or her natural element, as if a member of an imaginary body of marine cavalry
horse marine in American English
noun
1. (formerly)
a marine mounted on horseback or a cavalryman doing duty on shipboard
2.
a person out of his or her proper or natural place
Word origin
[1810–20]This word is first recorded in the period 1810–20. Other words that entered Englishat around the same time include: cleavage, dominance, triangulation, voodoo, zombie