A lower-working class person who betrays his or her class by behaviour or consumption. They believe their actions are perfectly normal but to others, these actions immediately identify their class of origin. Typically a classer betrays their lower working class origins through poor taste, bad haircut, absurdly rough accent or stupid ideas.
Look at that total classer! He thinks that walking around with his fat gut hanging over his trousers and shouting at his ugly girlfriend is normal behaviour