others to send, massive amounts of email to a single system or person, esp. with intent to crash or spam the recipient's system. Sometimes done in retaliation for a perceived serious offense. Mailbombing is itself widely regarded as a serious offense --- it can disrupt email traffic or other facilities for innocent users on the victim's system, and in extreme cases, even at upstream sites. 2. n. An automatic procedure with a similar effect. 3. n. The mail sent. Compare letterbomb, nastygram.