Definition of opisometer in US English:

opisometer

noun

  • A hand-held instrument for measuring the length of curved lines, especially on a map, usually having at its tip a small rotating wheel that is rolled along the line to be measured; a map-measurer.

Origin

Mid 19th century. From ancient Greek ὀπίσω backwards (from ὀπι- + a suffix forming adverbs indicating direction) + -meter.

Pronunciation

opisometer

/ˌɒpɪˈsɒmɪtə/