femtosecondn.
/ˈfɛmtəʊˌsɛk(ə)nd/, U.S. /ˈfɛmtoʊˌsɛkənd/ Chiefly Science.
A unit of time equal to one thousand-million-millionth of a second (10-15 second).
ΚΠ
1962 Newsweek 13 Aug. 47/1 There is a subatomic particle, for example, that decays in one hundred-thousandth of a femtosecond, give or take an attosecond.
1991 Alcalde (Univ. Texas) Jan.–Feb. 20/3 In 100 femtoseconds, light that can travel to the moon and back in just over two seconds covers a distance equal to the thickness of a single sheet of paper.
2006 C. W. Carey Amer. Scientists 410/1 The intense flashes of light lasted for only a few tens of femtoseconds.
This entry has been updated (OED Third Edition, March 2012; most recently modified version published online March 2022).
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n.1962