libration of the moon

: the combination of four libration effects that causes parts of the side of the moon turned to the earth to be alternately visible and invisible so that as much as 59 percent of the moon's entire surface can be observed from the earth

The Ultimate Dictionary 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