When the flight crew has their aircraft under control, everything is working normally and yet it still crashes into the ground, that's a "Controlled Flight Into Terrain".

Algeria's mountainous terrain restricts mobility.

Pluto's terrain shows remarkable variation including dark/bright regions and smooth/mountainous areas.

This latest discovery suggests that some pockets of the Martian terrain may be habitable and could contain some form of microbial life that escaped from the planet's freezing surface to the waters beneath.

When one announces "My my Tacubaya, if you don't know there don't go there", what this person actually refers to is the absence of governmental paternalism, and in certain areas of the capital, compels others to not attend those places they are unfamiliar with, where they are unaware of the terrain.

Unfamiliar terrain can be difficult to traverse.

The Grassland theme in Heroes of Might and Magic II is my favourite terrain theme in all of HoMM.

The rough terrain checked the progress of the hikers.

The terrain is mountainous.

The PRC's six-wheeled Zhurong robot rover touched down on the dunes of southern Utopia Planitia, a vast terrain in Mars's northern hemisphere. Zhurong is a name of an ancient fire god.