from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Something designed or intended for use in conjunction with another.
- n. An accessory software program that extends the capabilities of an existing application. Also called add-on, plug-in.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A plug-in.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a printed circuit that can be inserted into expansion slots in a computer to increase the computer's capabilities
add + in (Wiktionary)