a hinged or sliding door in a floor or ceiling

see "back doors"

a potentially less invasive CABG method currently under investigation; involves a three-inch incision under the left breast (versus the usual 12-inch incision through the breastbone). Trap door-style CABG is also performed on the beating heart, eliminating the need for the heart-lung machine

A secret way into a system that bypasses the security measures.

a mechanism built in to a system by its designer or administrator to give that person subsequent unauthorized access to the system

A way to bypass the normal login security and gain control of a computer without necessarily obtaining the owner's consent. If a backdoor is installed on a network-attached computer, a person anywhere on the Internet may be able to gain control of the computer without your knowledge or approval. A backdoor need not have malicious intent; e.g. operating systems are sometimes shipped by the manufacturer with privileged accounts for use by field service technicians or the vendor's maintenance programmers. However, they may also be used for intrusion by unauthorized persons. Also known as a "back door."