Noun, abbreviated from 'Homoeroticism, Yay!' The phrase
originated from the television programme 'Buffy the
Vampire Slayer,' and is used most commonly in various internet fandoms. It can also be an exclamation of glee.
The word is used to describe a homoerotic or homoromantic subtext between two characters, generally on a television show. Where one sees HoYay is, of course, extremely subjective, though in some cases it can be canon, not just subtext, as in the episode of 'Angel' wherein Spike says 'Angel and I were never intimate... apart from
that one time.'