Headlong and Whirlwind

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

Whirlwind and headlong are semantically related in breakneck topic. In some cases you can use "Whirlwind" instead an adjective "Headlong".

Whirlwind adjective - Moving, proceeding, or acting with great speed.

Headlong and whirlwind are semantically related in rapid topic. You can use "Headlong" instead an adjective "Whirlwind", if it concerns topics such as very fast.