What term describes a minor weakness or eccentricity in someone's character?

The term that best describes a minor weakness or eccentricity in someone's character is "foible." This word is often used to refer to a small, idiosyncratic trait that may be seen as quirky or endearing rather than detrimental. In many contexts, foibles highlight the humanity of individuals, showcasing that everyone has little quirks that make them unique. It implies a degree of light-heartedness and acceptance rather than severity or significance, which is why it is the most fitting term in this context.

The other terms, although sometimes used interchangeably, carry different connotations. A "flaw" generally refers to a more serious defect or inadequacy and suggests a negative impact on a person's overall character. A "fault" is similar to a flaw in that it conveys a more critical view of a person's character or abilities. "Imperfection" also denotes a lack of perfection but can refer to both minor and major issues, making it less specific when compared to "foible."