Etymology: ultra- + micrometer
: an extremely sensitive micrometer (as one capable of measuring to one millionth of an inch or less) frequently utilizing a variable capacitance that controls the frequency of an oscillator
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/ul'treuh muy krom"i teuhr/, n.
a micrometer calibrated to a very fine scale and capable of measuring extremely small magnitudes.
[1925-30; ULTRA- + MICROMETER]
Useful english dictionary. 2012.