The term "identity diffusion" refers to a part of the process of a person figuring out who they are. Typically, it is the part of adolescence when a person has not yet fully realized their social identity or defined their personality traits - and they are not actively seeking to. To develop and establish their identity they will need to make a series of choices and commitments.
Here are some examples of identity diffusion.
All of these are examples of identity diffusion because the people involved have not yet made their personal choices to solidify their identity.