A hybrid adjective of magic and cool; describing something or someone that is beyond what can normally be descibed as cool. This extra quality that has been recognised is put down to being magic hence the corruption of the usual term of magical in to magicool.
It should only be used in special occasions and not simply as a synonym for cool as it is a least three stronger than regular cool!
'Hey look over the Jack, can you see that unicorn with the neat shades and leather jacket?'
'Of course Jane, that's Leroy, he's magicool!'