Mipmap
Also said as Mip levels, Mips, Trilinear filtering
A stack of smaller, already blurred copies of each texture, and the graphics card picks the size that fits how far away the surface is. "Mip" comes from the Latin multum in parvo, much in a small space. Lance Williams described it in 1983.
Without them, a distant surface picks a few random pixels from a huge image, and the result shimmers as the camera moves. They also make rendering faster. They cost about a third more memory.
Say it
“Generate mipmaps for all world textures and use trilinear filtering, so the distant floor stops shimmering. Leave them off for pixel-perfect UI.”
Where you’ve seen it
The original PlayStation had no mipmapping in hardware, part of why its distant textures crawl as you move. The Nintendo 64 did have it.
Not to be confused with level of detail
Mipmaps swap a texture for a smaller version. Level of detail, or LOD, swaps a whole model for a simpler one. The idea is the same, but the things being swapped are different.