a tiny meteorite having a diameter of 10–40 micrometres, found esp in rainwater and seawater, having entered the atmosphere as a micrometeoroid (extremely small meteoroid)
micrometeorite in American English
(ˌmaɪkroʊˈmitiərˌaɪt)
noun
a very small meteorite, esp. one that drifts through the earth's atmosphere to the ground without becoming incandescent