split second

American  

noun

1. a fraction of a second.

2. an infinitesimal amount of time; instant; twinkling.

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split second British  

noun

1. an extremely small period of time; instant

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adjective

1. made or arrived at in an infinitely short time

   a split-second decision

2. depending upon minute precision

   split-second timing

split second Idioms  

1. An instant, a fraction of a second, as in Our best swimmer came in a split second before theirs. This expression alludes to a stop watch that has two second hands, one above the other, for timing more than one athlete or intervals of a race by a single athlete. Each hand can be stopped independently of the other, so a second can be “split” when one second hand stops a fraction of a second after the other. [c. 1880]

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Other Word Forms

• split-second adjective

Etymology

Origin of split second

First recorded in 1880–85

Example Sentences

For a split second, the lights, the crowd and his energy aligned perfectly.

From Los Angeles Times • Dec. 23, 2025

In a split second, Claire picks up, gets in her car, and heads for the highway, leaving her family in the dust.

From Salon • Dec. 3, 2025

A split second after “Action!” was called, I darted across the hall to a better spot and ran through the frame.

From The Wall Street Journal • Oct. 7, 2025

To be aware of, 'I'm on the ball here so this is what we trained' - but you have to think that in a split second.

From BBC • Sep. 13, 2025

It’s a stressful moment, but my favorite moment: the split second before the cacophony of sounds erupts and the race begins.

From "Red Flags and Butterflies" by Sheryl Azzam

Related Words

• blink of an eye
• millisecond
• nanosecond