Final answer:
Idle is best described as 'not busy', indicating a state where there is no activity or work being done, such as an idling engine or an individual without tasks.
Step-by-step explanation:
Idle means not busy. It often refers to a state where someone or something is not engaged in any activity or is not operating. For example, when an engine is running without being connected to any gears, it is said to be 'idling'. This means it's running but not doing any useful work. Similarly, when a person has nothing to do and is not actively engaged in any task, they can be described as being idle.