Webster's Revised Unabridged Dictionary · 1913

Headlong

Headlong (-long`; 115) , adverb

[Old English hedling, hevedlynge; prob. confused with English long, a. & adv.]

1.
With the head foremost; headforemost; head first; as, to fall headlong. — Acts i. 18
2.
Rashly; precipitately; without deliberation.
3.
Hastily; without delay or respite.

Headlong , adjective

1.
Rash; precipitate; as, headlong folly.
2.
Steep; precipitous. [Poetic]
Like a tower upon a headlong rock. — Byron