IPA: /ˈhɛd.lɒŋ/
KK: /ˈhɛdˌlɔŋ/
Moving or done with great speed and force, often without thinking carefully.
He ran headlong into the room, eager to share his news.
In a way that is fast and without thinking carefully, often leading to danger or mistakes.
She ran headlong into the street without looking for cars.
Headlong → It is formed from "head" (from Old English "heafod", meaning the upper part of the body) and "long" (from Old English "lang", meaning extended in space or time). The word "headlong" describes a manner of moving forward with the head leading, often in a reckless or hurried way.
Picture someone rushing forward with their 'head' leading the way, which helps you remember that 'headlong' means moving forward quickly and often recklessly.