headfirst
adverbUK /ˌhedˈfɜːst/
US /ˌhedˈfɝːst/
Moving with your head going first, before the rest of your body.
She jumped headfirst into the pool.
OTHER MEANINGS
2. Doing something very quickly and without thinking carefully first.
He rushed headfirst into the deal without reading the contract.
3. With great speed and force, often in a careless way.
The team charged headfirst into the new project.
4. In a way that shows no fear or hesitation.
She threw herself headfirst into learning the piano.