Webster's Revised Unabridged Dictionary · 1913

Mightily

Mightily , adverb

[From Mighty.]

1.
In a mighty manner; with might; with great earnestness; vigorously; powerfully.
Whereunto I also labor, striving according to his working, which worketh in me mightily. — Col. i. 29
2.
To a great degree; very much.
Practical jokes amused us mightily. — Hawthorne