プログレッシブ和英中辞典(第4版)の解説
ひっこみ【引っ込み】
引っ込みがちの人
〔遠慮がちな〕a person of retiring disposition／〔出不精の〕a stay-at-home
もう引っ込みがつかない
We have gone too far to retreat.／「It is too late [We are in too deep] to back out now.／We have crossed the Rubicon.
引っ込み思案
引っ込み思案の 〔内気な〕shy, retiring (in disposition)；〔冒険を好まない〕unadventurous
引っ込み思案で人前で意見を述べたがらない
He is shy and doesn't like to state his views in front of people.