Someone who resists change or stubbornly persists in a belief or opinion: Vance and Ingrid were known as old diehards who would hold out until the bitter end.

Ed and Jillian were a couple of "liberal-progressive" diehards who could only condemn conservatism.

A reference to anybody who is resistant to any kind of change, and reluctant to give up his or her beliefs, positions, or attitudes: They were diehard politicians who were locked into their uncooperative ways.

Dina's father was a diehard Republican and her mother was a diehard Democrat and neither one could agree on what should be done politically.