1.
pickled plum, umeboshi
A traditional Japanese preserved food made by salting and drying ume (Japanese apricot) fruits, often with red shiso leaves for color. Known for their extremely sour and salty taste.
梅干しは酸っぱい。
Umeboshi are sour.
Cultural note
梅干し is one of the most iconic traditional Japanese preserved foods. It has been a staple of the Japanese diet for centuries and is associated with health benefits, including aiding digestion and preventing fatigue.
日の丸弁当 (hinomaru bentou) is a simple lunch box with white rice and a single red 梅干し in the center, resembling the Japanese flag.
The sourness is so well-known that just thinking about 梅干し can make one's mouth water — a common example in Japanese physiology discussions.
Etymology
梅 (plum/Japanese apricot) + 干し (drying) — literally "dried plum." The し is the conjunctive form of the verb 干す (to dry).
Related Words
Related:
干す (to dry, to air)