Meaning of -FIRST in English

transcription, транскрипция: [ -fɜ:(r)st ]

-first combines with nouns like ‘head’ and ‘feet’ to indicate that someone moves with the part that is mentioned pointing in the direction in which they are moving.

He overbalanced and fell head first.

COMB in ADV : ADV after v

Collins COBUILD Advanced Learner's English Dictionary.      Английский словарь Коллинз COBUILD для изучающих язык на продвинутом уровне.