A cognitohazard is anything that is hazardous to perceive. For example, in the short story BLIT, there are certain patterns and images that cause the brain to shut down when you look at them, sort of like a computer crashing. A very benign real life example is earworms–really catchy songs that stick in your head after you listen to them. Just by listening to a song, it can cause you some form of harm (really just a mild annoyance, but still).
Another fun rabbit hole is infohazards. Things that are hazardous just to know. Like, you can see your nose, you’re aware of your breathing, and you can feel your tongue. Roko’s Basilisk is a hypothetical one with plenty of videos about it