Longman Dictionary of Contemporary English
The Collaborative International Dictionary
mailing list \mailing list\ n. A list of names and addresses to which advertising, solicitations of money, or other materials material sent in large quantities is mailed; -- it is usually used by comercial or charitable organizations. Mailing lists are often sold by organizations to other organizations, and are frequently used for targeted mailing, i. e., mailing to groups of people who are more likely htan the general population to respond as desired to the message in the mail.
Wiktionary
n. A collection of names and addresses used by an individual or an organization to send material to multiple recipients.
WordNet
n. a list of names and addresses to which advertising material is mailed
Wikipedia
A mailing list is a collection of names and addresses used by an individual or an organization to send material to multiple recipients. The term is often extended to include the people subscribed to such a list, so the group of subscribers is referred to as "the mailing list", or simply "the list".