Definition of signatures:
(n) :
A person's name, written by that person, used as identification or to signify approval of accompanying material, such as a legal contract.
(n) :
An act of signing one's name; an act of producing a signature.
(n) :
(Internet) Text (or images, etc.) appended to a user's emails, newsgroup posts, forum posts, etc. as a way of adding a personal touch or including contact details.
(n) :
(music) Signs on the stave indicating key and tempo, composed of the key signature and the time signature.
(n) :
(printing) A group of four (or a multiple of four) sheets printed such that, when folded, they become a section of a book.
(n) :
(computing) A pattern used for matching the identity of a virus, the parameter types of a method, etc.