a thing that is added to something else 附加物；附加装置 The company offers scuba-diving as an add-on to the basic holiday price. 这家公司提供戴水肺潜水活动，费用不含在基本度假费用内。 🔊🔊 add-on software (= added to a computer) 计算机附加软件
Oxford Collocations DictionaryAdd-on is used before these nouns:- module