perpetual motion machine

noun

: a device inherently impossible under the law of conservation of energy that can continue to do work indefinitely without drawing energy from external sources

The Ultimate Dicitonary Awaits

Expand your vocabulary and dive deeper into language with Merriam-Webster Unabridged.

1. Expanded definitions
2. Detailed etymologies
3. Advanced search tools
4. All ad-free

Discover what makes Merriam-Webster Unabridged the essential choice for true word lovers.

Start Your Free Trial Now