Webster's Revised Unabridged Dictionary · 1913

main

main (mān) , noun

[French main hand, Latin manus. See Manual.]

1.
A hand or match at dice. — Prior
2.
A stake played for at dice. [Obsolete] — Shakespeare
3.
The largest throw in a match at dice; a throw at dice within given limits, as in the game of hazard.
4.
A match at cockfighting.
My lord would ride twenty miles... to see a main fought. — Thackeray
5.
A main-hamper. [Obsolete] — Ainsworth

Main , noun

[Anglo-Saxon magen strength, power, force; akin to Old High German magan, Icelandic megin, and to English may, v. r103. See May, v.]

1.
Strength; force; might; violent effort. [Obsolete, except in certain phrases.]
There were in this battle of most might and main. — R. of Gl
He 'gan advance, With huge force, and with importable main. — Spenser
2.
The chief or principal part; the main or most important thing. [Obsolete, except in special uses.]
Resolved to rest upon the title of Lancaster as the main, and to use the other two... but as supporters. — Bacon
3.
(a) (Engineering) The great sea, as distinguished from an arm, bay, etc.; the high sea; the ocean.
(b)
(Engineering) The continent, as distinguished from an island; the mainland.
(c)
(Engineering) principal duct or pipe, as distinguished from lesser ones; esp. (Engineering), a principal pipe leading to or from a reservoir; as, a fire main.
Struggling in the main. — Dryden
Invaded the main of Spain. — Bacon
With might and main they chased the murderous fox. — Dryden
Collocations (3)
Forcing main , the delivery pipe of a pump.
For the main or In the main , for the most part; in the greatest part.
With might and main or With all one's might and main , with all one's strength; with violent effort.

Main (mān) , adjective

[From Main strength, possibly influenced by Old French maine, magne, great, Latin magnus. Compare Magnate.]

1.
Very or extremely strong. [Obsolete]
That current with main fury ran. — Daniel
2.
Vast; huge. [Obsolete]
The main abyss. — Milton
3.
Unqualified; absolute; entire; sheer. [Obsolete]
It's a man untruth. — Sir W. Scott
4.
Principal; chief; first in size, rank, importance, etc.; as, the main reason to go; the main proponent.
Our main interest is to be happy as we can. — Tillotson
5.
Important; necessary. [Obsolete]
That which thou aright Believest so main to our success, I bring. — Milton
That Maine which by main force Warwick did win. — Shakespeare

Main , adverb

[See Main, a.]

Very; extremely; as, main heavy. [Obsolete or Low]
I'm main dry. — Foote