What does the term 'diffident' mean regarding someone's personality?

The term 'diffident' refers to a personality characterized by a lack of self-confidence or hesitance in asserting oneself. Someone who is diffident often feels shy or timid, particularly in social situations or when required to express their opinions. This aligns with the definition of being 'shy,' which encompasses feelings of reserve and a tendency to avoid the spotlight. The other terms do not fit the definition: being confident suggests an absence of shyness, while boldness and arrogance imply a level of assertiveness that contradicts the essence of being diffident. Thus, the correct answer accurately captures the meaning of the word, highlighting a personality that is more reserved and introspective rather than outgoing or assertive.