Systems & Memory
Setuid
Also: setuid bit, SUID
A permission that makes a program run with its owner's rights, usually root, no matter who starts it.
In more detail
It lets ordinary users do narrow privileged jobs such as changing a password. It also makes the program a doorway: arguments and environment variables from the user flow into a root process, so a bug there is an escalation. In ls -l it shows as an s in the owner's execute position.