a kind of magnetic compass, fitted with a small prism, that enables the heading to be read while sighting
prismatic compass in American English
noun
a hand compass equipped with sights and prisms to permit aiming the instrument at a point and at the same time reading the compass direction of the point
Word origin
[1850–55]This word is first recorded in the period 1850–55. Other words that entered Englishat around the same time include: boneyard, clear-cut, heavyweight, overprint, runoff