add-on

/ˈædɒn/ noun [C]

Definition

› something extra that is added to a product to make it better: DVDs often include bonus endings and other add-ons.an add-on to sth Many companies offer legal expenses cover as an add-on to home insurance policies. add-on parts/products/services

› IT a piece of computer equipment or software that is added to a computer so that the computer can do more or different things: an add-on to sth It would require an add-on to a browser to make it all work. add-on devices/features/software

(Definition of add-on noun from the Cambridge Business English Dictionary © Cambridge University Press)