black cap—
1. a warbler:
- We followed a pleasant path through trees and soon found ourselves listening to the sweet bubbling song of a black cap.
2. (UK hist.) a cap put on by a judge before sentencing a person to death:
- He acquitted two men and then placed the black cap on his head and sentenced the other two to death.
black hat—
1. (coll.) the bad party in a situation (from the color of hat traditionally worn by the bad character in Western films):
- Past entertainment had a moral content—the white hats won and the black hats lost.
2. (Austral. sl.) a new immigrant:
- I’d never let it be said that a black hat had cut me out.