split second

noun

1. a fraction of a second.

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

split second

noun

1. an extremely small period of time; instant

adjective

1. made or arrived at in an infinitely short time

   a split-second decision

2. depending upon minute precision

   split-second timing

Other Word Forms

• split-second adjective

Word History and Origins

Origin of split second¹

First recorded in 1880–85

Idioms and Phrases

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]

Related Words

• blink of an eye www.thesaurus.com
• millisecond 
• nanosecond