An unscheduled airplane landing that is made under circumstances (engine failure or adverse weather) not under the pilot's control WordNet 3.0 & Open English WordNet

A forced landing is a landing by an aircraft made under factors outside the pilot's control, such as the failure of engines, systems, components, or weather which makes continued flight impossible. Wikipedia

An emergency landing or crash landing is a premature landing made by an aircraft in response to an emergency involving an imminent or ongoing threat to the safety and operation of the aircraft, or involving a sudden need for a passenger or crew on board to terminate the flight. Wikipedia

Landing by an aircraft made under factors outside the pilot's control. Wikipedia Disambiguation

Unplanned landing by an aircraft. Wikipedia Disambiguation

Aircraft landing made in response to a crisis Wikidata

Type of emergency landing Wikidata

A sudden landing of an aircraft, made in case of an on-board emergency or another reason requiring an immediate landing. Wiktionary

Landing made in an emergency. Wiktionary (translation)