split-second

1 of 2

adjective

split-sec·​ond ˈsplit-ˈse-kənd 

1

: occurring in a split second

a split-second decision

2

: extremely precise

split-second timing

split second

2 of 2

noun

: a fractional part of a second : flash

Synonyms of split-second

Adjective

• instantaneous
• immediate
• instant

Noun

• minute
• second
• moment
• heartbeat

Examples of split-second in a Sentence

Adjective

a day trader who is used to making split-second decisions

Noun

In a split second, it was all over.

a devastating accident can cause everything in your life to change in a split second

Recent Examples on the Web

Adjective

Athletes should never have to make a split-second decision between following a pace vehicle or trusting the official course. —Ryan Gaydos, FOXNews.com, 2 Mar. 2026

Finally, the complicated intersections of Houston demand split-second decision-making, a skill not all drivers have, but the construction of a commercial truck requires for safety. —Wyles Daniel, USA TODAY, 27 Feb. 2026

Noun

Lee Harvey Oswald folding under Jack Ruby’s bullet—a split second that hardens into our collective memory. —Christopher Anderson, Vanity Fair, 27 Feb. 2026

Judges score the flips and spins, including pretzel-like shapes with skis splayed or crossed, before the skiers pull up at the last split second and slam skis-first into the landing area, kicking up a spray of snow. —ABC News, 16 Feb. 2026

Word History

First Known Use

Adjective

1944, in the meaning defined at sense 1

Noun

1912, in the meaning defined above

Rhymes for split-second

• beckoned
• reckoned
• second
• seconde
• femtosecond
• microsecond
• millisecond
• nanosecond
• picosecond

Kids Definition

split second

1 of 2 noun

: a small fraction of a second : flash

split-second

2 of 2 adjective

1

: occurring in a split second

a split-second decision

2

: extremely precise

split-second timing