A wave of unpredictable size, speed, or direction; (now) specifically an exceptionally large wave in the open ocean that far exceeds those encountered in prevailing sea conditions, with heights reaching 25 to 30 metres (approx. 82 to 98 feet).
Origin
1960s.
Definition of rogue wave in US English:
rogue wave
noun
A wave of unpredictable size, speed, or direction; (now) specifically an exceptionally large wave in the open ocean that far exceeds those encountered in prevailing sea conditions, with heights reaching 25 to 30 metres (approx. 82 to 98 feet).