Fromzepto- +‎second.

zeptosecond (pluralzeptoseconds)

2. (metrology) AnSI unit oftime equal to 10⁻²¹seconds. Symbol:zs

   Alternative form:zs(symbol)

   Holonyms:attosecond <femtosecond <picosecond <nanosecond <microsecond <millisecond <centisecond <decisecond <second <decasecond <minute <hectosecond <kilosecond <hour <day <week <megasecond <fortnight <month <year <gigasecond <century <kiloannum,kiloyear,millennium <terasecond <mega-annum,megayear <petasecond <giga-annum,gigayear <exasecond <zettasecond <yottasecond <ronnasecond <quettasecond

   Meronyms:quectosecond <rontosecond <yoctosecond

   • 2025 May 23, King Chimera (chimera_4212), “N/A”, inx.com‎^[1]:

     Hxh son all day any week and any hour any minute any second, any millisecond, any microsecond, any nanosecond any picosecond any femtosecond, any attosecond, anyzeptosecond, any yoctosecond, any rontosecond, any quectosecond

   • 2025 October 7, baldigaming285, somesillysprunker, “can we all laugh at this guy”, inreddit.com‎^[2]:

     sprunker: "ok ill delay the update by 67 years, 67 months, 67 days, 67 hours, 67 seconds, 67 deciseconds, 67 centiseconds, 67 milliseconds, 67 microseconds, 67 nanoseconds, 67 picoseconds, 67 femtoseconds, 67 attoseconds, 67zeptoseconds, 67 yoctoseconds, 67 rontoseconds, 67 quectoseconds, and 67... plank^[sic] time????".

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