From Longman Dictionary of Contemporary Englishmicrosecondmi‧cro‧sec‧ond /ˈmaɪkrəʊˌsekənd $ -kroʊ-/ noun [countable] TMone millionth of a second
Examples from the Corpus
microsecond• Those chords of searching bewilderment in the finale were timed to a microsecond and projected an awesome tingle of fear.• Knocking heads until the last microsecond.• Otherwise, you may find that, within microseconds, they have been indelibly marked with the territorial's initials. 