Headlong means rushing forward without thinking or planning, often recklessly or out of control. When you run headlong down a hill, you're moving so fast that you might tumble or crash. When someone dives headlong into a swimming pool, they plunge in head first with complete commitment.

The word captures that feeling of momentum where you can't or won't stop yourself. A student might rush headlong into a difficult project without reading the instructions first, then realize they've made extra work for themselves. A knight in an old story might charge headlong into battle, brave but perhaps not very cautious.

Headlong can describe physical movement or decision-making. Running headlong means literally moving with your head leading the way. But making a headlong decision means jumping into something without thinking it through. If you rush headlong into an argument, you're speaking without considering your words carefully.

The word suggests speed, intensity, and a lack of caution. It's not always bad: sometimes diving headlong into a new adventure or challenge takes courage. But headlong actions can lead to tumbles, mistakes, or surprises you didn't plan for.