Someone who either:
1. Wants to return the dollar to a gold standard,
2. Wants to use gold as money in addition to the dollar, or
3. Collects or invests in gold, silver, and/or other precious metals.
Gold bugs are sometimes associated with paranoia, conspiracy theories, 9/11 "truthers," survivalism, tax protesters, racism, anti-semitism, and the far right.
As a gold bug, I can tell you that gold is REAL money, and worthless fiat paper money is a fraud.