A micrometer (Symbol μm ) is worth 10^-6 = 0,   000  001 Meter.

One used before the name micron ; it was withdrawn from the international Système in 1968, but is always very used nowadays. The symbol which it used (µ) is now reserved for the prefix IF “micro”.

Another meaning

A micrometer (or Micrometer caliper) is also a measuring device length.

Simple: Micrometer Zh-min-nan: Bi-bí