n. 1 a a person's name, initials, or mark used in signing a letter, document, etc. b the act of signing a document etc. 2 archaic a distinctive action, characteristic, etc. 3 Mus. a = key signature. b = time signature. 4 Printing a a letter or figure placed at the foot of one or more pages of each sheet of a book as a guide for binding. b such a sheet after folding. 5 US directions given to a patient as part of a medical prescription. signature tune esp. Brit. a distinctive tune used to introduce a particular programme or performer on television or radio.
[ med.L signatura (LL = marking of sheep), as SIGNATORY ]