A questioner said:

Found in a home. First floor, located in a room off a kitchen. About 6 feet off the ground and the crescent shape is open into the wall.

More from the owner: We were looking around the house to find all the outlets and found this in a room connected to the kitchen. We think it’s for wiring behind the wall but seems weird based on the location

Some of the people opinions on it:

This is for wiring for something wall mounted. Generally placed behind wall mounted tvs. The slot is for your data or coax cable pull, or auxiliary audio or whatever.
It’s for wiring behind the wall.
There should be something similar below it at normal outlet height. You’re supposed to mount a tv over the upper outlet and run the wiring through the wall to hide it.
This is for running data or cable tv or satellite hookup wires. So you would have a tv plugged in to the outlet and then the cable connecting it to your media provider runs through the gap. Also cables to your sound system, dvd player, game console etc. can also run through.
Usually for a wall mount TV to route the cables so you don’t see them
6 ft off the ground
Have similar. There is a hall closet on the other side. Looks like the PO had a cable box in there .
For behind wall wires. A lot of people like a kitchen tv and looks a lot better than a PVC pipe sticking out of the wall.
What do you think it is? Let us know in the comment!