blue line / (historical) Short for 青線地帯(あおせんちたい) (aosenchitai): Aosen (districts in Japan where prostitution and the sex industry flourished)

a western swamphen

red-root amaranth

indigo, dark blue / indigo-colored dye

(attributive, chemistry) Synonym of シアン化 (shian-ka, “cyanide”)

Synonym of シアン化物 (shian kabutsu, “cyanide”) (chemistry: any compound containing the CN group)

a female given name

(Internet slang, networking) Synonym of ブルートゥース (“Bluetooth”)

(slang) having sex in the open air

a skyscraper (tall building)