headlong

excessively quick; "made a hasty exit"; "a headlong rush to sell"

with the head foremost; "a headfirst plunge down the stairs"; "a headlong dive into the pool"

with the head foremost; "the runner slid headlong into third base"

at breakneck speed; "burst headlong through the gate"

in a hasty and foolhardy manner; "he fell headlong in love with his cousin"