Being reserved or shy; introverted and reluctant to be forward in social situations.
彼は引っ込み思案で、初対面の人と話すのが苦手だ。
He's shy and bad at talking to people he meets for the first time.
子どもの頃は引っ込み思案だったが、学校の演劇で自信がついた。
I was shy as a child, but I gained confidence through the school play.
面接で引っ込み思案な態度を取ると積極性がないと見なされることがある。
If you act withdrawn in an interview, you may be seen as lacking initiative.