Yaoi
The word Yaoi (pronounced /jaoi/, sound like "Yah-Oh-ee" rather than "Yow-ee" or "Ya-oy", all three vowels are pronounced) was originally used to refer to fan manga (such as doujinshi) that focused on homosexual relationships between male characters, especially two bishōnen - the manga equivalent of slash.
The term is an acronym derived from the Japanese phrase 「ヤマなし、オチなし、意味なし」 ( yama nashi, ochi nashi, imi nashi ), meaning "no climax, no punch line, no meaning." Its target audience, readership and creators are almost exclusively young to middle-age women.
A common reason as to why many females are attracted to yaoi is that it is said to be a means for females to fully enjoy romance without feeling pressure or competition from the presence of a romantic/sexual female character in the story, not necessarily because they are supporters of gay rights.
Nowadays, the term is often used in a general way to refer to male-male sexual or romantic content anywhere in the galaxy of anime, manga and fan fiction based on these; usually of a more hard-core nature than the now-obsolete shōnen-ai.
The term "BL" (Boy's Love) is more often used in Japan than the term Yaoi. There exists a large mainstream market for Boys' Love comics in Japan, as well as a flourishing dōjinshi market. In recent years several popular Japanese BL works have been commercially translated and imported to English-speaking countries by companies such as Be Beautiful and Digital Manga Publishing. Currently-available works include Kazuma Kodaka's Kizuna, and Only the Ring Finger Knows by Satoru Kinnagi and Hotaru Odagiri. Whether such works will have comparable poplarity in English-speaking countries remains to be seen.
Over the years, gay-themed comic strips inspired by and referred to as yaoi have been adapted as a sub-culture in North America, with writings and art displayed on websites devoted to it. Notable American yaoi comics include the web comic Boy Meets Boy by K. Sandra Fuhr, hosted on Keenspot.
Some common subjects of the American yaoi subculture include the boys of Trigun, Cardcaptor Sakura, Final Fantasy, Gravitation, Gundam Wing, Naruto, Prince of Tennis, Weiss Kreuz, Yu-Gi-Oh!, and Yu Yu Hakusho. Generally speaking, if a series features attractive male characters, it will attract yaoi fans. Thus a large amount actually comes from male-oriented shounen & seinen demographics. This sometimes causes conflict because fanboys are, stereotypically, intensely homophobic and dislike such themes. For example, one resistive force against the yaoi culture, surprisingly, comes not from conservatives but from fans of UC Gundam (fans of original Gundam), which had also self acclaimed as "UC elitist". This is primarily because Gundam series features male main characters. A prime example is Gundam Wing, in which for about 8 months, doing an unfiltered google image search for gundam would result in "hard" yaoi.