Pin  —n. 1 small thin pointed piece of metal with a round or flattened head used (esp. In sewing) for holding things in place, attaching one thing to another, etc. 2 peg of wood or metal for various purposes. 3 (in idioms) something of small value (not worth a pin). 4 (in pl.) Colloq. Legs. —v. (-nn-) 1 a (often foll. By to, up, together) fasten with a pin or pins. B transfix with a pin, lance, etc. 2 (usu. Foll. By on) put (blame, responsibility, etc.) On (a person etc.). 3 (often foll. By against, on, etc.) Seize and hold fast.  pin down 1 (often foll. By to) bind (a person etc.) To a promise, arrangement, etc. 2 force (a person) to declare his or her intentions. 3 restrict the actions of (an enemy etc.). 4 specify (a thing) precisely. Pin one's faith (or hopes etc.) On rely implicitly on. [latin pinna point etc.]