Webster's Revised Unabridged Dictionary · 1913

What

What (hwot) , pron., a., & adv.

[Anglo-Saxon hwat, neuter of hwā who; akin to Old Saxon hwat what, OFries. hwet, Dutch & LG. wat, German was, Old High German waz, hwaz, Icelandic hvat, Swedish & Danish hvad, Gothic hwa. r182. See Who.]

1.
As an interrogative pronoun, used in asking questions regarding either persons or things; as, what is this? what did you say? what poem is this? what child is lost?
What see'st thou in the ground? — Shakespeare
What is man, that thou art mindful of him? — Bible (KJV) - Psalm viii. 4
What manner of man is this, that even the winds and the sea obey him! — Matt. viii. 27
2.
As an exclamatory word: -- (a) Used absolutely or independently; -- often with a question following.
What welcome be thou. — Chaucer
What, could ye not watch with me one hour? — Matt. xxvi. 40
(b)
Used adjectively, meaning how remarkable, or how great; as, what folly! what eloquence! what courage!
What a piece of work is man! — Shakespeare
O what a riddle of absurdity! — Young

What in this use has a or an between itself and its noun if the qualitative or quantitative importance of the object is emphasized.

(c)
Sometimes prefixed to adjectives in an adverbial sense, as nearly equivalent to how; as, what happy boys!
What partial judges are our love and hate! — Dryden
3.
As a relative pronoun
(a)
Used substantively with the antecedent suppressed, equivalent to that which, or those [persons] who, or those [things] which; -- called a compound relative.
With joy beyond what victory bestows. — Cowper
I'm thinking Captain Lawton will count the noses of what are left before they see their whaleboats. — Cooper
What followed was in perfect harmony with this beginning. — Macaulay
I know well... how little you will be disposed to criticise what comes to you from me. — J. H. Newman
(b)
Used adjectively, equivalent to the... which; the sort or kind of... which; rarely, the... on, or at, which.
See what natures accompany what colors. — Bacon
To restrain what power either the devil or any earthly enemy hath to work us woe. — Milton
We know what master laid thy keel, What workmen wrought thy ribs of steel. — Longfellow
(c)
Used adverbially in a sense corresponding to the adjectival use; as, he picked what good fruit he saw.
4.
Whatever; whatsoever; what thing soever; -- used indefinitely.
What after so befall. — Chaucer
Whether it were the shortness of his foresight, the strength of his will,... or what it was. — Bacon
5.
Used adverbially, in part; partly; somewhat; -- with a following preposition, especially, with, and commonly with repetition.
What for lust [pleasure] and what for lore. — Chaucer
Thus, what with the war, what with the sweat, what with the gallows, and what with poverty, I am custom shrunk. — Shakespeare
The year before he had so used the matter that what by force, what by policy, he had taken from the Christians above thirty small castles. — Knolles
What time the morn mysterious visions brings. — Pope

What , noun

Something; thing; stuff. [Obsolete]
And gave him for to feed, Such homely what as serves the simple clown. — Spenser

What , interrog. adv.

Why? For what purpose? On what account? [Obsolete]
What should I tell the answer of the knight. — Chaucer
But what do I stand reckoning upon advantages and gains lost by the misrule and turbulency of the prelates? What do I pick up so thriftily their scatterings and diminishings of the meaner subject? — Milton