Etymology: Middle English, from Old English cǣg; akin to Old Frisian kēi key
Date: before 12th century
a. a usually metal instrument by which the bolt of a lock is turned
b. any of various devices having the form or function of such a key
a. a means of gaining or preventing entrance, possession, or control
b. an instrumental or deciding factor
a. something that gives an explanation or identification or provides a solution <the key to a riddle> b. a list of words or phrases giving an explanation of symbols or abbreviations c. an aid to interpretation or identification ; clue d. an arrangement of the salient characters of a group of plants or animals or of taxa designed to facilitate identification e. a map legend 4. a. (1) cotter pin (2) cotter b. a keystone in an arch c. a small piece of wood or metal used as a wedge or for preventing motion between parts 5. a. one of the levers of a keyboard musical instrument that actuates the mechanism and produces the tones b. a lever that controls a vent in the side of a woodwind instrument or a valve in a brass instrument c. a part to be depressed by a finger that serves as one unit of a keyboard 6. samara 7. a system of tones and harmonies generated from a hierarchical scale of seven tones based on a tonic <the key of G major> 8. a. characteristic style or tone b. the tone or pitch of a voice c. the predominant tone of a photograph with respect to its lightness or darkness 9. a decoration or charm resembling a key 10. a small switch for opening or closing an electric circuit <a telegraph key> 11. the set of instructions governing the encipherment and decipherment of messages 12. a free-throw area in basketball • keyed adjective • keyless adjective II. verb Date: 14th century transitive verb 1. to lock with or as if with a key ; fasten: as a. to secure (as a pulley on a shaft) by a key b. to finish off (an arch) by inserting a keystone 2. to regulate the musical pitch of 3. to bring into harmony or conformity ; make appropriate ; attune <remarks keyed to a situation> 4. to identify (a biological specimen) by a key 5. to provide with identifying or explanatory cross-references <instructions keyed to accompanying drawings — John Gartner> 6. to make nervous, tense, or excited — usually used with up <was keyed up over her impending operation> 7. keyboard — often used with in 8. to be essential to ; play the most important part in <defense keyed the victory> intransitive verb 1. to use a key 2. to observe the position or movement of an opposing player in football in order to anticipate the play — usually used with on 3. keyboard III. adjective Date: 1913 important, fundamental <key issues> IV. noun Etymology: Spanish cayo, from Taino Date: 1697 a low island or reef; specifically any of the coral islets off the southern coast of Florida V. noun Etymology: by shortening & alteration from kilo Date: 1968 slang a kilogram especially of marijuana or heroin
New Collegiate Dictionary. 2001.