key¹ / kē/ • n. (pl. keys ) 1. a small piece of shaped metal with incisions cut to fit the wards of a particular lock, and that is inserted into a lock and turned to open or close it. ∎  a similar implement for operating a switch in the form of a lock, esp. one operating the ignition of a motor vehicle. ∎ short for key card. ∎  an instrument for grasping and turning a screw, peg, or nut, esp. one for winding a clock or turning a valve. ∎  a pin, bolt, or wedge inserted between other pieces, or fitting into a hole or space designed for it, so as to lock parts together. 2. one of several buttons on a panel for operating a typewriter, word processor, or computer terminal. ∎  a lever depressed by the finger in playing an instrument such as the organ, piano, flute, or concertina. ∎  a lever operating a mechanical device for making or breaking an electric circuit, for example, in telegraphy. 3. a thing that provides a means of gaining access to or understanding something: the key to Jack’s behavior may lie submerged in his unhappy past. ∎  an explanatory list of symbols used in a map, table, etc. ∎  a set of answers to exercises or problems. ∎  a word or system for solving a cipher or code. ∎  the first move in the solution of a chess problem. ∎  Comput. a field in a record that is used to identify that record uniquely. 4. Mus. a group of notes based on a particular note and comprising a scale, regarded as forming the tonal basis of a piece or passage of music: the key of E minor. ∎  the tone or pitch of someone's voice: his voice had changed to a lower key. 5. the dry winged fruit of an ash, maple, or sycamore maple, typically growing in bunches; a samara. 6. Basketball the keyhole-shaped area marked on the court near each basket, comprising the free-throw circle and the foul line.• adj. of paramount or crucial importance: she became a key figure in the suffragette movement.• v. (keys, keyed / kēd/ ) [tr.] 1. enter or operate on (data) by means of a computer keyboard: she keyed in a series of commands | [intr.] a hacker caused considerable disruption after keying into a vital database. 2. [tr.] (usu. be keyed) fasten (something) in position with a pin, wedge, or bolt: the coils may be keyed into the slots by fiber wedges. ∎  (key something to) make something fit in with or be linked to: this optimism is keyed to the possibility that the U.S. might lead in the research field. ∎  (key someone/something into/in with) cause someone or something to be in harmony with: to those who are keyed into his lunatic sense of humor, the arrival of any Bergman movie is a major comic event. 3. word (an advertisement in a particular periodical), typically by varying the form of the address given, so as to identify the publication generating particular responses. 4. inf. be the crucial factor in achieving: Ewing keyed a 73–35 advantage on the boards with twenty rebounds.5. [tr.] vandalize a car by scraping the paint from it with a key: somebody could key your car and not get punished.PHRASES: in (or out of) key in (or out of) harmony: this vaguely uplifting conclusion is out of key with the body of his book.PHRASAL VERBS: key someone up (usu. be keyed up) make someone nervous, tense, or excited, esp. before an important event.DERIVATIVES: keyed adj.key·er n.key·less adj.key² • n. a low-lying island or reef, esp. in the Caribbean. Compare with cay.