Not to be confused with Notelock or Fingerlock.
Mind block is a term used to describe when a player repeatedly fails or misses on what was a previously easy section of a beatmap, often as a result of retrying said beatmap repeatedly. The term is named "mind block" since the event that it describes creates the sensation that the player's brain (mind) has been figuratively "blocked" from successfully obtaining a full combo or completing the aforementioned section.
Mind block is often caused by heavy build-up of "useless muscle memory" from constant, repeated, and quick retrying of a beatmap. Although no official science or research has been conducted on this specific phenomenon in osu!, it is widely believed by the community that during mind block, the player's mind is often bored, burned-out, or tired of doing the same patterns and hearing the same few seconds of music, that it struggles to focus and pay attention, and thus struggles to develop new muscle memory.
Many players often remedy and prevent mind block by taking breaks or playing different beatmaps, as it is common consensus among osu! players that giving the mind a break from osu! will allow it to rest, reflect, and recuperate. Likewise, many players will often switch playing beatmaps after so many attempts before mind block occurs to allow for better focus on other beatmaps.