- occurring, done, or completed in an instant: an instantaneous response.
- existing at or pertaining to a particular instant: the instantaneous position of the rocket.
- occurring with almost no delay; immediate
- happening or completed within a momentinstantaneous death
- occurring at or associated with a particular instant
- equal to the limit of the average value of a given variable as the time interval over which the variable is considered approaches zeroinstantaneous velocity
1640s (implied in instantaneously), formed in English from Medieval Latin *instantaneus, from instantem (see instant (n.)) on model of spontaneous. Related: Instantaneousness.