double blossom; double-flowered
Refers to flowers with multiple layers of petals, often used in gardening and botanical contexts.
This cherry tree has double blossoms and is very showy.
Double-flowered roses have many petals and look luxurious.
Compound of 八重 (yae, 'multilayered') + 咲き (zaki, 'blooming', from 咲く). The exact historical derivation is straightforward.