addon

Noun

add-on (plural add-ons)

1. (attributive, sometimes) Something which can be appended to something else.
   • Payments made before an add-on sale must be allocated entirely to the previous contract or contracts.1969, Edward D. Giacomini, California Retail Installment Sales, page 172

   Synonyms:

   addition

2. A software extension or hardware peripheral that provides additional functions or customization for a core application or system.
   • Microdrives that can hold several gigabytes (see Figure 2.20) have been available as add-ons for portable devices.2010, Kenneth Baldauf, Ralph Stair, Succeeding with Technology, page 77
3. Additional chips that can be purchased at specific times in tournament play.
4. Synonym of expansion pack.

   Synonyms:

   expansion pack