add-onsale
nounUK /ˈæd ɒn seɪl/
US /ˈæd ɑːn seɪl/
An add-onsale is when you buy something extra along with the main thing.
The toy came with an add-onsale of extra batteries.
OTHER MEANINGS
2. A special price for buying an extra item together with a main item.
The add-onsale made the second pair of shoes half price.
3. The act of selling an extra product to someone who is already buying something.
The clerk made an add-onsale by offering a phone case.
4. An additional item offered for sale next to a main product.
The add-onsale items were displayed near the register.