Wikipedia
A spamtrap is a honeypot used to collect spam.
Spamtraps are usually e-mail addresses that are created not for communication, but rather to lure spam. In order to prevent legitimate email from being invited, the e-mail address will typically only be published in a location hidden from view such that an automated e-mail address harvester (used by spammers) can find the email address, but no sender would be encouraged to send messages to the email address for any legitimate purpose. Since no e-mail is solicited by the owner of this spamtrap e-mail address, any e-mail messages sent to this address are immediately considered unsolicited.
The term is a compound of the words "spam" and "trap", because a spam analyst will lay out spamtraps to catch spam in the same way that a fur trapper lays out traps to catch wild animals. The provenance of this term is unknown, but several competing anti-spam organizations claim trademark over it.