aftermarket

Short definition from Wiktionary

Noun

1. 1
   The market for further goods and services, such as replacement parts and accessories, subsequent to the sale of a product such as an automobile or computer.
2. 2
   The industry that serves that market.
3. 3
   Trading activity in a security immediately following its initial offering to the public.

Verb

1. 1
   To sell goods or services in the aftermarket.