plug-in       
noun [ C ] uk/ˈplʌɡ.ɪn/ us/ˈplʌɡ.ɪn/
 (计算机程序的)插件
a small computer program that makes a larger one work faster or have more features
  The plug-in lets users quickly search their e-mail inboxes and connect with contacts.
 Plug-ins can be used to support virus scanning, file compression and file encryption software.
 Compare: patch noun (COMPUTER)
 - More examples
 - It works through a small browser plug-in.
 - This is a plug-in, that is a small program that adds some specified capability to an internet browser.
 - If you need to edit something, you just find the appropriate plug-in and go.