形容词

1. 羞怯的;胆怯的;缺乏自信的
Someone who is diffident is rather shy and does not enjoy talking about themselves or being noticed by other people.

1. lacking self-confidence

e.g. stood in the doorway diffident and abashed
problems that call for bold not timid responses
a very unsure young man

Synonym: shytimidunsure

2. showing modest reserve

e.g. she was diffident when offering a comment on the professor's lecture