This, is exactly what the title says: my personal definition of a personal definition.
A personal definition of something - anything, really - is the way you conceive and/or perceive the subject or situation at hand, based on your views of the world and reality in general. Thus, going to the very bottom of it, your (personal) definitions of everything are strongly based on your upbringing and (past) experiences.
This is true in each and every case, this one included.