jack oak

noun

1

: blackjack sense 5

2

: an extremely variable oak (Quercus ellipsoidalis) of east central North America having leaves with sharply pointed lobes and ashy gray turbinate to goblet-shaped acorn cups with persistent dull pubescence

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