IPA: /hɛdˈfɔːrməʊst/
KK: /hɛdˈfɔrˌmoʊst/
In a way that involves moving forward with the head leading, often used to describe a sudden or reckless action.
He jumped headforemost into the water without thinking.
Headforemost → It is formed from "head" (from Old English "heafod", meaning the upper part of the body or leader) and "foremost" (from Old English "foran" meaning in front and "most" meaning the greatest or highest degree). The word "headforemost" means with the head in front or leading the way.
Think of the 'head' as the leader and 'foremost' meaning in front — so 'headforemost' describes going in with the head leading the way.