head·first 
/ˈhɛdˈfɚst/ adverb
/ˈhɛdˈfɚst/ adverb 1 : with the head leading
▪ She dove into the water headfirst. — compare feetfirst 2 : without taking time to think about your actions
▪ She rushed into the relationship headfirst.
▪ She dove into the water headfirst. — compare feetfirst
▪ She rushed into the relationship headfirst.
— headfirst adjective
▪ a headfirst dive/slide
▪ a headfirst dive/slide
