noun
a thing that is added to sth else :
The company offers scuba-diving as an add-on to the basic holiday price.
add-on software (= added to a computer)
noun
a thing that is added to sth else :
The company offers scuba-diving as an add-on to the basic holiday price.
add-on software (= added to a computer)
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005