kill two birds with one stone, do one task and finish two or more goals (literally, “one stone, two birds”)

(obsolete) being surprised twice / (obsolete) more specifically, describes the appearance of a woman who has a beautiful figure from behind but has an ugly face

(grammar) a verbal conjugation class in which the verb stem ends in -i and consists of four alternating bases: -i, -iru, -ire, and -iyo/-iro

Kyūjitai form of 三位一体 (“Trinity”)

Rome wasn't built in a day

(idiomatic, proverb) be quick on the uptake, understand the whole situation from just a few clues

Alternative form of 十二単

(Christianity) the Trinity

an anthology of one hundred poems by one hundred poets, one poet for each poem

short for 小倉百人一首 (Ogura Hyakunin Isshu): a famous "one hundred poems anthology", used as the basis of certain card games