IPA: /hɛdˈfɜrst/
KK: /hɛdˈfɜrst/
In a manner where the head is leading or foremost, often used to describe a sudden or reckless action.
He jumped headfirst into the pool without thinking.
Headfirst → It is formed from "head" (from Old English "heafod", meaning the upper part of the body) and "first" (from Old English "fyrst", meaning foremost or at the front). The word "headfirst" describes a position where the head is leading or going in first, typically in a downward motion.
Think of leading with your 'head' — that's why 'headfirst' means going in with your head first.