Plain English Meaning
Picking the best available place to put the airplane down when you can no longer keep flying. You weigh the options in front of you and choose the one most likely to leave you and your passengers walking away.
Full Definition
The pilot's deliberate choice of where to attempt a forced or precautionary landing when continued flight is not possible, based on a comparison of available surfaces for survivability, controllability of the touchdown, and post-landing access to help.
Context Anchor
Seen in emergency landing training, especially when discussing what to do after engine trouble or when an off-airport landing may be needed.
Derivation
comes from the Latin terra, meaning land or . In it refers to the features below the airplane — fields, , trees, roads, slopes. Selection emphasises that this is an active choice, not whatever happens to be underneath you when the engine quits.