observatory (place where celestial bodies are observed)

Taiping Heavenly Kingdom

an outdoor bath, often at a naturally occurring hot spring

(linguistics) sound shift / (linguistics) sound shifts from Old Japanese to Modern Japanese, especially those which are preserved in historical kana usage.

changing school

astronomical unit

2.5D / (by extension, fandom slang) belonging to a grey area between "2D" (anime, etc.) and "3D" (live-action, etc.), such as voice actors

(informal) Synonym of 転売屋 (tenbaiya, “reseller”)

(Buddhism) clairvoyance, one of the 六神通 (rokujinzū, “six abhijñā (“higher power”)”)

(sex, informal) impotence