Headlong and Unsagacious

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

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

Headlong and unsagacious are semantically related in unthinking topic. You can use "Headlong" instead an adjective "Unsagacious", if it concerns topics such as unmindful of future consequences.