electronic mail

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun E-mail.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Computers) a message transmitted from one computer to another, accessible by means of a mail reading program on the receiving computer. The message may have one or many intended recipients, and may be directed by the sending program to one or to multiple receiving computers. The message is typically in the form of a computer file, and may be a simple ASCII text, or any other type of binary coded information.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun uncountable E-mail (the system).
• noun countable, rare An e-mail.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (computer science) a system of world-wide electronic communication in which a computer user can compose a message at one terminal that can be regenerated at the recipient's terminal when the recipient logs in