This refers to the two points in the year when the Sun appears to stop moving north or south in the sky, marking the solstices.

* Summer solstice: The Sun reaches its highest point in the sky and appears to "stop" its northward movement.

* Winter solstice: The Sun reaches its lowest point in the sky and appears to "stop" its southward movement.

So, while the term "sunstop" itself is not a common astronomical term, "solar standstill" captures the essence of the Sun appearing to pause its apparent motion at the solstices.