When the textures of two parallel planes are competing to be rendered in the same space. Can occur either because they were placed atop one another, or because the camera is distant enough that the two planes are essentially atop one another.
eww... when that sliding door opened, it started z-fighting with the wall.
Ususally refered to as (Pathetic Noise), <pathetic noise>, *pathetic noise* or Squeak, the pathetic noise is a high-pitched squeak noise produced by pushing air through pursed lips (not sucking). The air is pushed from the mouth with use of cheek muscles (not the lungs/diaphram).
The noise can take much practice and a long time to master, but once perfected it can become part of everyday speech quite easily.
Origionally a part of the Spacko language, this has become a central point for many conversations in plain English too.
It can have many meanings (anger, jubilation, sorrow, etc), depending what context it is used in.