- The definition of instantaneous is something that happens right away.
If you ask for water and water immediately appears that very second, this is an example of something instantaneous.
instantaneous definition by Webster's New World
- done, made, or happening in an instant
- done or made without delay; immediate: an instantaneous reply
- existing at a particular instant
Origin: Midieval Latin instantaneus
instantaneous definition by American Heritage Dictionary
- Occurring or completed without perceptible delay: Relief was instantaneous.
- Done or made as quickly or directly as possible: an instantaneous reply to my letter.
- Present or occurring at a specific instant: instantaneous velocity; instantaneous pressure.
Origin: From Medieval Latin īnstantāneus, from Latin īnstāns, īnstant-, present; see instant.
- in·stanˌta·neˈi·ty noun
- inˌstan·taˈne·ous·ly adverb
- inˌstan·taˈne·ous·ness noun