Instant :: Instant (a.) A point in duration; a moment; a portion of time too short to be estimated; also, any particular moment..
Instant :: Instant (a.) A day of the present or current month; as, the sixth instant; -- an elliptical expression equivalent to the sixth of the month instant, i. e., the current month. See Instant, a., 3..
Instantaneous :: Instantaneous (a.) Done or occurring in an instant, or without any perceptible duration of time; as, the passage of electricity appears to be instantaneous..
Instantaneous :: Instantaneous (a.) At or during a given instant; as, instantaneous acceleration, velocity, etc..
Instanter :: Instanter (a.) Immediately; instantly; at once; as, he left instanter..
Instantly :: Instantly (adv.) Without the least delay or interval; at once; immediately.
Instantly :: Instantly (adv.) With urgency or importunity; earnestly; pressingly.