1. Inclined to act on impulse rather than thought.
2. Motivated by or resulting from impulse: such impulsive acts as hugging strangers; impulsive generosity.
3. Having force or power to impel or incite; forceful.
4. Physics Acting within brief time intervals. Used especially of a force.
im·pulsive·ness, im′pul·sivi·ty n.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.