ripe persimmon
Refers to a fully ripened persimmon fruit. Often used in the proverb 熟柿が落ちるのを待つ (wait for a ripe persimmon to fall), meaning to wait for an opportunity.
In autumn, the ripe persimmons in the garden become sweet.
Compound of 熟 (juku, 'ripen') and 柿 (shi, 'persimmon').