Deviant means different things to different people.
To the religious in the North vinefields it is similar to calling someone a "heretic", someone who looks up to the light instead of hiding from it.
To the Tan Nomads it is someone who wants to provoke.
To the Blue Deviants of Deviant Isle it is a title of honor. Though they call themselves 'Deviants' as a jab towards the Heretic title the religious give them. But to the Blue Deviants the only real way to earn the title of "Deviant" is you must have reached space.
But 'Deviant' has the same definition everywhere.
"One who thinks differently."