microinch
/ˈmaɪkroʊˌɪntʃ/
noun
- A unit of length equal to one millionth of an inch, used for very precise measurements.
- A microinch is so small that it is invisible to the naked eye.
- The surface of the metal was polished to a smoothness of a few microinches.
- Engineers measure the thickness of a coating in microinches.