Merriam-Webster Collegiate Dictionary - pin

 I. noun  Etymology: Middle English, from Old English ~n (akin to Old High German pfinn peg), perhaps from Latin ~na quill, feather — more at pen  Date: before 12th century  1.  a. a piece of solid material (as wood or metal) used especially for fastening things together or as a support by which one thing may be suspended from another  b. obsolete the center peg of a target; also the center itself  c. something that resembles a ~ especially in slender elongated form an electrical connector ~  d.  (1) one of the pieces constituting the target in various games (as bowling)  (2) the peg at which a quoit is pitched  (3) the staff of the flag marking a hole on a golf course  e. a peg for regulating the tension of the strings of a musical instrument  f. the part of a key stem that enters a lock  g. a belaying ~  2.  a.  (1) a very thin small pointed metal ~ with a head used especially for fastening cloth  (2) little, trifle bother them all! I don't care a ~ about them — Bram Stoker  b. an ornament or emblem fastened to clothing with a ~  c.  (1) bobby ~  (2) hair~  (3) safety ~  3. leg — usually used in plural wobbly on his ~s  4. a fall in wrestling  II. transitive verb  (~ned; ~ning)  Date: 14th century  1.  a. to fasten, join, or secure with a ~  b. to hold fast or immobile  c. to present (a young woman) with a fraternity ~ as a pledge of affection  2.  a. fasten ~ned his hopes on a miracle ~ the blame on someone else  b. to assign the blame or responsibility for ~ the robbery on a night watchman  c. to define or determine clearly or precisely — usually used with down it is hard to ~ down exactly when things changed — Katharine Whittemore  3.  a. to make (a chess opponent's piece) unable to move without exposing the king to check or a valuable piece to capture  b. of a wrestler to secure a fall over (an opponent)  III. adjective  Date: 1523  1. of or relating to a ~  2. of leather having a grain suggesting the heads of ~s PIN  abbreviation personal identification number