A secondary punisher is a concept in operant conditioning that describes punishers that acquire their effect as a result of conditioning instead of being naturally negative stimuli. In behaviorism, a punisher is something aversive or negative that makes the likelihood of a behavior decrease.
Your parents taking away your privileges for getting bad grades is a type of punishment. Primary punishers are innately punishing in that we are naturally and biologically averse to them.
Examples of primary punishers include physical pain, being burned, feeling too cold or too hot, and being hungry. You don't have to learn that being burned is a bad thing - you immediately know it the first time you touch something too hot. Secondary punishers are things that we don't innately have negative connections with so we must be conditioned to associate them with being aversive.
For example, if you had no association, experience, or knowledge of a speeding ticket then it wouldn't be a punisher. It would just be a piece of paper. But once you learn what a speeding ticket is and what it represents (wasting a lot of money!) then it becomes a punishment in that it makes the undesired behavior (speeding) less likely to occur in the future. We aren't born with an innate response to exposure to a speeding ticket- it's a secondary punisher because we learn and are conditioned to know what it means. This concept applies to reinforcers as well in that secondary reinforcers are learned rather than being naturally present.