Webster's Revised Unabridged Dictionary · 1913

Instant

Instant , adjective

[Latin instans, -antis, present participle of instare to stand upon, to press upon; pref. in- in, on + stare to stand: compare French instant. See Stand.]

1.
Pressing; urgent; importunate; earnest.
Rejoicing in hope; patient in tribulation; continuing instant in prayer. — Rom. xii. 12
I am beginning to be very instant for some sort of occupation. — Carlyle
2.
Closely pressing or impending in respect to time; not deferred; immediate; without delay.
Impending death is thine, and instant doom. — Prior
3.
Present; current.
The instant time is always the fittest time. — Fuller

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

Instant , adverb

Instantly. [Poetic]
Instant he flew with hospitable haste. — Pope

Instant , noun

[French instant, from Latin instans standing by, being near, present. See Instant, a.]

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.
There is scarce an instant between their flourishing and their not being. — Hooker
2.
A day of the present or current month; as, the sixth instant; -- an elliptical expression equivalent to the sixth of the month instant, that is, the current month. See Instant, a., 3.