|Origin:||headling 'head-first' (14-17 centuries), from head + -ling 'in a particular direction'|
if you rush headlong into something, you start doing it too quickly without thinking carefully
with your head first and the rest of your body following [= headfirst]:
I fell headlong into a pool of icy water.
very quickly, without looking where you are going:
Mortimer almost ran headlong into a patrol.