If you ask for water and water immediately appears that very second, this is an example of something instantaneous.
An instantaneous reply to my letter.
Relief was instantaneous.
An instantaneous reply.
Instantaneous velocity; instantaneous pressure.
Origin of instantaneous
- From Medieval Latin īnstantāneus from Latin īnstāns īnstant- present instant
From American Heritage Dictionary of the English Language, 5th Edition
- New Latin, 17th century