Bearly Contained is an achievement in Halo: The Master Chief Collection. It is awarded for activating the sixth Halo: Combat Evolved Anniversary Terminal on 343 Guilty Spark. The achievement is worth 5 gamerpoints and can be unlocked on any difficulty.
The sixth terminal is found while riding the third elevator that leads out of the underground facility. The terminal is above the doorway leading into the elevator room. It can be reached by activating the elevator, then timing it correctly and jumping off onto the platform below (there is only one possible attempt due to the lack of elevator controls on the top floor).
The name of the achievement comes from a discussion on the Halo Waypoint with Catalog, where a user joked that the crashed starship shown in the terminal was not built by "dogs, cats, [or] certain bears", followed by Catalog confirming that ursus sapiens (i.e. "wise bear") have not been seen in the galaxy.