Short for ヘボン式ローマ字綴り方 (Hebon-shiki rōmaji tsuzurikata):

Short for 訓令式ローマ字綴り方 (kunrei-shiki rōmaji tsuzurikata): a Romanization method of Japanese, adopted by Cabinet order in 1937

betting system where one bets regarding the winner / betting ticket where one bets regarding the winner

(chemistry) projection

(algebra) monomial expression

(offensive, Internet slang) Alternative form of 子供部屋おじさん

(offensive, Internet slang) a man whose age is greater than about thirty or forty who lives in one's child room and with one's parent(s).

single room

double room

being alicyclic (of a class of organic compounds)