If you move head-first in a particular direction, your head is the part of your body that is furthest forward as you are moving.
例句
He had apparently fallen head-first down the stairwell...他显然是从楼梯井口一头栽了下来。My mate dived headfirst through a window and I ran down the hallway.我的同伴从窗口一头扎了下去,而我则沿着走廊跑。
英英词典释义
Adjective
1. with the head foremost;
"a headfirst plunge down the stairs""a headlong dive into the pool"