back door; backdoor
noun
1
the anus and rectum UK, 1694.
2
in sports, the advancement of a team in a playoff situation as a result of the actions of another team US, 1952.
3
in a group motorcyle ride, the last rider in the group, usually the most experienced; the final citizens' band radio user in a convoy US, 1976.
4
a surreptitious way of entering a protected system or website, made possible by a weakness in the system US, 1990.► go out the back doorto back down from a confrontation US, 1981