Self-appointed (adjective)

Having appointed oneself to a position or role without formal approval.

Origin:

Combination of self and appointed, meaning to assign oneself to a position or role without formal approval.

Examples:

1. He is a self-appointed leader of the group.
2. The self-appointed guardian of the community's morals.
3. She considered herself a self-appointed authority on the subject.
4. The self-appointed task force was formed to address the problem.
5. The group rejected the proposal of the self-appointed representative.