instantaneous

adjective

in·​stan·​ta·​neous ˌin(t)-stən-ˈtā-nē-əs 

-nyəs

1

: done, occurring, or acting without any perceptible duration of time

death was instantaneous

2

: done without any delay being purposely introduced

took instantaneous corrective action

3

: occurring or present at a particular instant

instantaneous velocity

instantaneity

ˌin-ˌstan-tə-ˈnē-ə-tē 

ˌin(t)-stən-tə-ˈnē-

noun

instantaneously

ˌin(t)-stən-ˈtā-nē-əs-lē 

-nyəs-lē

adverb

instantaneousness noun

Synonyms

• immediate
• instant
• split-second
• straightaway

Examples of instantaneous in a Sentence

We got an almost instantaneous response from the company.

the thunder following the flash of lightning was nearly instantaneous

Recent Examples on the Web

The date mechanism is particularly noteworthy for its instantaneous jump at midnight. —Bhanu Chopra, Forbes, 22 Jan. 2025

The permit allowed for 406 colony-forming units per 100 milliliters or less as the instantaneous maximum. —Angela Palermo, Idaho Statesman, 18 Jan. 2025

Rejection Sensitive Dysphoria Traits People with RSD experience an overwhelming, instantaneous, negative emotional reaction to even mild forms of rejection.2 Criticisms that other people might brush off or feel sad about for a short period feel catastrophic to a person with RSD. —Sarah Bence, Verywell Health, 14 Jan. 2025

Essentially, the standards call for new tankless (sometimes called instantaneous) gas water heaters to use less energy than the least efficient models currently available, according to the Appliance Standards Awareness Project. —Addy Bink, The Hill, 6 Jan. 2025

Word History

Etymology

borrowed from Medieval Latin instantāneus, from instant-, instans "moment, point of time," + Latin -āneus, suffix forming adjectives from temporal adverbs — more at instant entry 1

Note: Regarding the suffix -āneus see the etymology and note at spontaneous.

First Known Use

1651, in the meaning defined at sense 1

Kids Definition

instantaneous

adjective

in·​stan·​ta·​neous ˌin(t)-stən-ˈtā-nē-əs 

-nyəs

1

: happening in an instant

2

: done without delay

instantaneously adverb

instantaneousness noun