HEADFIRST
headfirst, headlong
(adjective) with the head foremost; “a headfirst plunge down the stairs”; “a headlong dive into the pool”
headlong, headfirst
(adverb) with the head foremost; “the runner slid headlong into third base”
Source: WordNet® 3.1
Etymology
Adverb
headfirst (not comparable)
With the head in front; headlong.
Rashly; precipitately; without deliberation; hastily.
Synonyms
• (with the head in front): headforemost, headlong
Adjective
headfirst (not comparable)
With the head in front; headlong.
Source: Wiktionary
Head`first", Head`fore"most`, adv.
Definition: With the head foremost.
Source: Webster’s Unabridged Dictionary 1913 Edition