Top Definition
The smallest MEASURABLE time unit known today, 1x10^(-24) seconds. Obviously, smaller units of time exist, but proper equipment and methodology for measuring them does not yet exist. Light travels 2.9979x10^(-16) meters in one yoctosecond, not the 3.33km stated above.
Learn to multiply. This isn't even an 'urban' word, so why is it defined here?
by iNsAniTy August 05, 2005

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The smallest unit of time known today. It is on septillionth of a second, or about 0,000000000000000000000001 second(10^-24).
Light can travel a distance of approximately 3.33 kilometers in one yoctosecond.
by Tom Something July 15, 2005

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