n. & v.
n. (pl. keys) 1 an instrument, usu. of metal, for moving the bolt of a lock forwards or backwards to lock or unlock. 2 a similar implement for operating a switch in the form of a lock. 3 an instrument for grasping screws, pegs, nuts, etc., esp. one for winding a clock etc. 4 a lever depressed by the finger in playing the organ, piano, flute, concertina, etc. 5 (often in pl.) each of several buttons for operating a typewriter, word processor, or computer terminal, etc. 6 what gives or precludes the opportunity for or access to something. 7 (attrib.) essential; of vital importance (the key element in the problem). 8 a place that by its position gives control of a sea, territory, etc. 9 a a solution or explanation. b a word or system for solving a cipher or code. c an explanatory list of symbols used in a map, table, etc. d a book of solutions to mathematical problems etc. e a literal translation of a book written in a foreign language. f the first move in a chess-problem solution. 10 Mus. a system of notes definitely related to each other, based on a particular note, and predominating in a piece of music (a study in the key of C major). 11 a tone or style of thought or expression. 12 a piece of wood or metal inserted between others to secure them. 13 the part of a first coat of wall plaster that passes between the laths and so secures the rest. 14 the roughness of a surface, helping the adhesion of plaster etc. 15 the samara of a sycamore etc. 16 a mechanical device for making or breaking an electric circuit, e.g. in telegraphy.
v.tr. (keys, keyed) 1 (foll. by in, on, etc.) fasten with a pin, wedge, bolt, etc. 2 (often foll. by in) enter (data) by means of a keyboard. 3 roughen (a surface) to help the adhesion of plaster etc. 4 (foll. by to) align or link (one thing to another). 5 regulate the pitch of the strings of (a violin etc.). 6 word (an advertisement in a particular periodical) so that answers to it can be identified (usu. by varying the form of address given). key industry an industry essential to the carrying on of others, e.g. coal-mining, dyeing. key map a map in bare outline, to simplify the use of a full map. key money Brit. a payment demanded from an incoming tenant for the provision of a key to the premises. key-ring a ring for keeping keys on. key signature Mus. any of several combinations of sharps or flats after the clef at the beginning of each staff indicating the key of a composition. key up (often foll. by to, or to + infin.) make (a person) nervous or tense; excite. keyer n. keyless adj.
[ OE cg, of unkn. orig. ]