A mattress protector.

(slang) A final portion of a beverage drink, often with coffee drinks or alcoholic mixes, that will fill a cup to the top.

plural of topper-offer

(slang) A police car with red lights mounted on top.

(UK) A double-deck bus with an open, or partially open, top deck.

(archaic) top hat; chimney-pot hat

A decorative ornament placed on the top of a Christmas tree, often in the form of a star or angel.