Translation

自信のなさ / 内気さ / 遠慮がちな態度

Meaning

Diffidence is a shy, hesitant lack of confidence, especially when someone is unsure about speaking, acting, or putting themselves forward. It is more formal than shyness.

Examples

• 彼女は会議で少し自信なさげに話しました。
  She spoke with some diffidence at the meeting.
• 彼の遠慮がちな態度は能力の低さではありません。
  His diffidence is not a lack of ability.