Guard

From Memory Alpha, the free Star Trek reference.

A guard is an individual who is assigned to watch over or protect something. On Earth Starfleet and later Federation starships, this task is usually given to a security officer, often one with a lower title than security chief.

The Malcorian Lanel once helped William T. Riker escape by distracting the guard outside the room where Riker was being held. Before she helped him, however, she made him fulfill one of her fantasies: having sex with an alien. (TNG: "First Contact")

While investigating a five-year-old murder, Odo posted a guard in the Deep Space 9's infirmary to guard Quark, who was the only lead but was struggling for life. (DS9: "Necessary Evil")

Two Jem'Hadar guards were posted in the station's brig while Kira Nerys and Rom were being held there, the latter scheduled for execution the next day. However, Quark and Tora Ziyal disabled the officer stationed in the security office and Quark shot both guards. (DS9: "Sacrifice of Angels")