Definition of Self involves becoming awareness, becoming the Truth. You can't agree with it intellectually, it's not the same as actually becoming it. This is Enlightenment.
Definition requires comparison. Everything in the dictionary is defined by being not everything else. For self-definition you have to find out what is not you.. you let it all go until you're left with just awareness, basically. But I don't think this is what the OP was referring to so I'll stop here.
In terms of definition socially and in our world.. definitions are just a system of agreement between people. No one really knows whether the colour blue you see is the same as what I see, and this applies to everything. No one knows for sure except what is present in their bubble of experience, but definitions help us to separate and communicate through things efficiently.
I think it's a waste of time to worry about how you're defined socially or in the eyes of others. The more important definition is Self definition, finding out who/what you are.
Know Thy Self.
