add-on

noun

Definitions of add-on

(CONTRACTS LAW), a clause in an instalment contract whereby goods that have already been purchased are used as security for payment on goods which are subsequently purchased under the contract.

Northstar announced that it has been awarded another add-on to the multi million contract awarded by L-3 MAPPS Inc.

additional

computer software which is run through another software application

A new experimental Firefox add-on can help you see exactly who's following you online.