What is the term for turbulence that occurs less than 1/3 of the time?

The term used to describe turbulence that occurs less than 1/3 of the time is indeed "occasional turbulence." This classification is part of the broader categorization of turbulence intensity, where different terms are used to convey the frequency of occurrence. Occasional turbulence specifically indicates that the phenomenon is not present most of the time, aligning with the definition that describes its sporadic nature.

In contrast, intermittent turbulence refers to turbulence that is present at irregular intervals but can occur more frequently than occasional turbulence, typically more than 1/3 of the time. Continuous turbulence signifies that turbulence is consistently present and typically affects the aircraft for an extended period, while severe turbulence describes extreme conditions that can cause significant disruptions and is not based on frequency but rather intensity and impact on flight. Understanding these terms is crucial for pilots and meteorologists as they assess flight conditions and communicate expected turbulence levels to ensure safety.