A spam trap, sometimes called a honeypot, is an email address created or repurposed specifically to identify senders who do not follow good permission and hygiene practices. These addresses never opt in to anything, so any mail arriving at them is by definition unsolicited or the product of a scraped or purchased list.
There are two main types. Pristine traps are addresses that were never used by a real person and are seeded onto the web to catch scrapers. Recycled traps are former real addresses that a provider abandoned and later reactivated as traps - hitting one means you are mailing contacts who stopped engaging long ago.
Spam traps are run by mailbox providers and anti-abuse organizations, and hitting them carries serious consequences. It can land your sending domain or IP on a blocklist, tank your inbox placement, and in severe cases get your account terminated by your email service provider. Because traps are invisible, you cannot simply remove them by name.
The only reliable defense is prevention: use confirmed opt-in, never buy or scrape lists, verify addresses before importing, and remove long-inactive contacts through re-engagement or sunsetting. Good list hygiene is what keeps traps off your list, because you cannot detect them directly once they are there.