a. Happening at the same instant. C. Darwin. [ 1913 Webster ]

n. [ F. instant, fr. L. instans standing by, being near, present. See Instant, a. ] [ 1913 Webster ]

1. A point in time; a moment; a portion of time too short to be estimated; also, any particular moment; as, the situation may change in an instant. [ 1913 Webster +PJC ]

There is scarce an instant between their flourishing and their not being. Hooker. [ 1913 Webster ]

2. 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.

Syn. -- Moment; flash; second. [ 1913 Webster ]

a. [ L. instans, -antis, p. pr. of instare to stand upon, to press upon; pref. in- in, on + stare to stand: cf. F. instant. See Stand. ] [ 1913 Webster ]

1. Pressing; urgent; importunate; earnest. [ 1913 Webster ]

Rejoicing in hope; patient in tribulation; continuing instant in prayer. Rom. xii. 12. [ 1913 Webster ]

I am beginning to be very instant for some sort of occupation. Carlyle. [ 1913 Webster ]

2. Closely pressing or impending in respect to time; not deferred; immediate; without delay. [ 1913 Webster ]

Impending death is thine, and instant doom. Prior. [ 1913 Webster ]

3. Present; current. [ 1913 Webster ]

The instant time is always the fittest time. Fuller. [ 1913 Webster ]

☞ The word in this sense is now used only in dates, to indicate the current month; as, the tenth of July instant. [ 1913 Webster ]

adv. Instantly. [ Poetic ] [ 1913 Webster ]

Instant he flew with hospitable haste. Pope. [ 1913 Webster ]

n. [ Cf. F. instantanéité. ] Quality of being instantaneous. Shenstone. [ 1913 Webster ]

a. [ Cf. F. instantané. ] [ 1913 Webster ]

1. Done or occurring in an instant, or without any perceptible duration of time; as, the passage of electricity appears to be instantaneous. [ 1913 Webster ]

His reason saw
With instantaneous view, the truth of things. Thomson. [ 1913 Webster ]

2. At or during a given instant; as, instantaneous acceleration, velocity, etc. [ 1913 Webster ]

Instantaneous center of rotation (Kinematics), 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. --
Instantaneous axis of rotation (Kinematics), 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.

-- In`stan*ta"ne*ous*ly, adv. -- In`stan*ta"ne*ous*ness, n. [ 1913 Webster ]

‖adv. [ L., vehemently, earnestly. See Instant, n. & a. ] Immediately; instantly; at once; as, he left instanter. [ 1913 Webster ]

adv. 1. Without the least delay or interval; at once; immediately. Macaulay. [ 1913 Webster ]

2. With urgency or importunity; earnestly; pressingly. “They besought him instantly.” Luke vii. 4.

Syn. -- Directly; immediately; at once. See Directly. [ 1913 Webster ]