Definition of "Headlong" :

adjective: with the head foremost

"A headlong dive into the pool."

adjective: excessively quick

"A headlong rush to sell."

adverb: with the head foremost

"The runner slid headlong into third base."

adverb: in a hasty and foolhardy manner

"He fell headlong in love with his cousin."

adverb: at breakneck speed

"Burst headlong through the gate."