- A notched and grooved, usually metal implement that is turned to open or close a lock. (noun)
- A similar device used for opening or winding: the key of a clock; a can that has a key attached. (noun)
- A means of access, control, or possession. (noun)
- A vital, crucial element. (noun)
- A set of answers to a test. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.