kan man också säga, "jag vill inte definiera mig själv" or "jag vill inte definiera själv"?
In english what is the difference between "define myself" and "define me"? (The latter is not accepted.)
In English, if you're talking about doing something to yourself specifically, then you wouldn't use "me". You could say "I don't want it/you/they to define me", but NOT "I don't want to define me". The correct way would be "I don't want to define myself". :-)
I think illumillama's comment on this page is helpful, it gives you the other perspective.
I'll add that it works the same with other reflexive verbs, like Jag tvättar mig 'I wash myself' so it's how it works in general.