Portmanteau of ‘straight’ and ‘dyke.’ Used to indicate a straight woman who, to the onlooker’s surprise (see: the traditional use of ‘Sike/syke’), appears as a butch lesbian.
Syke is said (or yelled) as sign of opposition to what was last said by the one who says (or yells) it. Basically, if I say I have a nice girl, followed by a syke, it means my chick is a whore. :-) You can also say "not", "nae" or "or...".
Ryan : Your bae gave me a call, she wanted to see me.
Marley : For what?
Ryan : She was flirtingwith me.
Marley is really surprised!
Ryan : Syke!
Marley slaps Ryan and walks away.
Someone who is syke-otic is completely obsessed and totally in love with Oliver Sykes, the lead singer of the band Bring Me The Horizon. Oli Sykes is completely and utterly beautiful and has an amazing screaming voice and normal voice with the hottest accent ever. Lots of usually female fans but also some male fans describe them selves as "syke-otic".
Jasmine: Charlotte, your so syke-otic! You have a whole wall of just oli Sykes pictures!