Webster's Revised Unabridged Dictionary · 1913

Amain

Amain ({not transcribed}) , adverb

[Prefix a- + main. See 2d Main, n.]

1.
With might; with full force; vigorously; violently; exceedingly.
They on the hill, which were not yet come to blows, perceiving the fewness of their enemies, came down amain. — Milton
That striping giant, ill-bred and scoffing, shouts amain. — T. Parker
2.
At full speed; in great haste; also, at once.
They fled amain. — Holinshed

Amain , transitive verb

[French amener. See Amenable.]

(Nautical) To lower, as a sail, a yard, etc.

amain , intransitive verb

(Nautical) To lower the topsail, in token of surrender; to yield.