An adjective refering to something which is so spectacular, it is almost majestic. Not to be used lightly. Originated from a misunderstanding involving the fictional character "Max Hoyland" from the Australian soap "Neighbours" whereby the sentence "Max is key in this episode" was exclaimed by a viewer and was misinterpretted for "Max is keyin".
That episode of Neighbours was so keyin.
by Jonathan Masefield December 15, 2006