headfirst

adv

1. (not-comparable)With the head in front; headlong.
2. (not-comparable)Rashly; precipitately; without deliberation; hastily.

   “Sheffield was not going to stop being Sheffield just because he had dived headfirst into the lusts of the flesh.”

   “Over the past two years, Silicon Valley’s leaders and investors — many of whom had once forsworn involvement in weapons and war — have plunged headfirst into the military industrial complex.”

adj

1. (not-comparable)With the head in front; headlong.