Headlong and Unable

Headlong adjective - Acting or done with excessive or careless speed.

Unable and headlong are semantically related. In some cases you can use "Unable" instead an adjective "Headlong".

Unable adjective - Lacking qualities (as knowledge, skill, or ability) required to do a job.

Headlong and unable are semantically related. Sometimes you can use "Headlong" instead an adjective "Unable".