Added 10 October 2026 micrometre /ˈmaɪkɹəˌmiːtə/ noun Categories: Obscure Words noun ! Definition from Wiktionary (CC BY-SA). Pronunciation from Wiktionary, via Kaikki.org. More about micrometre at Wordnik → Where our words come from → An SI and mks unit of measure, the length of one-millionth of a metre. Symbol: μm, um, μ. Related Words: micrometermicronmillimetremillimetermillimètremicromolemicrounitmicromillimetremillimicronmicromolmicroinchmicromillimeter Back to today's word