How is "erratic" best defined?

The term "erratic" is best defined as unpredictable and eccentric. When something is described as erratic, it suggests a lack of consistency or a tendency to vary unpredictably. This can apply to behavior, performance, or even natural phenomena, indicating that such things do not follow a regular pattern. For instance, a person exhibiting erratic behavior may act in unexpected ways without any clear rationale, reflecting unpredictability. Thus, the definition closely aligns with the notion of eccentricity, which encompasses unusual or quirky traits.

In contrast, the other definitions provided do not capture the essence of the term. "Consistently stable" and "methodical and regular" imply reliability and predictability, which are the opposite of what "erratic" conveys. "Poorly planned" suggests a lack of structure or foresight rather than unpredictability, which does not fit the specific connotations of "erratic." Therefore, "unpredictable and eccentric" truly encapsulates the meaning of the word in question.