instantaneous

Occurring or completed without perceptible delay.

Done or made as quickly or directly as possible.

Present or occurring at a specific instant.

Done or produced in an instant; occurring or acting without any perceptible lapse of time.

In mech., existing in or referring to an instant of time; momentary: as, instantaneous position, displacement, velocity, acceleration, etc. (that is, the position, etc., at any instant).

Done or occurring in an instant, or without any perceptible duration of time.

At or during a given instant

in a plane or in a plane figure which has motions both of translation and of rotation in the plane, is the point which for the instant is at rest.

in a body which has motions both of translation and rotation, is a line, which is supposed to be rigidly united with the body, and which for the instant is at rest. The motion of the body is for the instant simply that of rotation about the instantaneous axis.

Occurring, arising, or functioning without any delay; happening within an imperceptibly brief period of time.