The symbol for the yen monetary unit as written in Japanese (and pronounced "en"), or the symbol for the yuan renminbi monetary unit as used in China. In Japanese, the Kanji 円 is used instead. The Kanji literally means "round," "circle," or "yen" (!) in English according to JDIC.
The Kanji character is Unicode character number 0x5186, and can be produced with 円 in HTML. No shorthand HTML entity for the Kanji is available to Westerners, though: ¥ resolves to ¥.