[ mahy-krom-i-ter ]
/ maɪˈkrɒm ɪ tər /


any of various devices for measuring minute distances, angles, etc., as in connection with a telescope or microscope.
Also called mike. micrometer caliper. a precision instrument with a spindle moved by a finely threaded screw, for the measurement of thicknesses and short lengths, commonly used by machinists for turning shafts or boring holes.

Nearby words

  1. micromere,
  2. micrometastasis,
  3. micrometeorite,
  4. micrometeoroid,
  5. micrometeorology,
  6. micrometer screw,
  7. micromethod,
  8. micrometre,
  9. micrometry,
  10. micromicro-

Also especially British, mi·crom·e·tre.

Origin of micrometer

First recorded in 1660–70; micro- + -meter

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for micrometre


/ (ˈmaɪkrəʊˌmiːtə) /


a unit of length equal to 10 –6 metreSymbol: μm Former name: micron


/ (maɪˈkrɒmɪtə) /


any of various instruments or devices for the accurate measurement of distances or angles
Also called: micrometer gauge, micrometer calliper a type of gauge for the accurate measurement of small distances, thicknesses, diameters, etc. The gap between its measuring faces is adjusted by a fine screw, the rotation of the screw giving a sensitive measure of the distance moved by the face
Derived Formsmicrometry, nounmicrometric (ˌmaɪkrəʊˈmɛtrɪk) or micrometrical, adjective

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for micrometre



1660s, from micro- + -meter. Originally a telescope attachment; from 1884 as a craftsman's fine measuring tool. Related: Micrometry; micrometric.

Online Etymology Dictionary, © 2010 Douglas Harper

Science definitions for micrometre


[ mī-krŏmĭ-tər ]

A device for measuring very small distances, angles, or objects, especially one based on the rotation of a finely threaded screw, as in relation to a microscope.


[ mīkrō-mē′tər ]

A unit of length in the metric system equal to one millionth (10-6) of a meter. Also called micron
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.