WordNet Dictionary
Webster's 1913 Dictionary\Post"mas`ter\, n. 1. One who has charge of a station for the accommodation of travelers; one who supplies post horses. 2. One who has charge of a post office, and the distribution and forwarding of mails.
Computing DictionaryThe electronic mail contact and maintenance person at a site connected to the internet or uucpnet. Often, but not always, the same as the admin. The Internet standard for electronic mail (rfc 822) requires each machine to have a "postmaster" address; usually it is aliased to this person. See also webmaster.