/kap"euhr/ , n.
1. a person or thing that caps.
2. Also called topper . something that completes or adds to what has preceded it: The capper was that we didn't know each other after all.
3. Slang. an informer, esp. for gamblers.
4. Slang. a by-bidder at an auction.
[ 1350-1400 (for sense "cap maker"); 1580-90 (for def. 1); ME; see CAP 1 , -ER 1 ]