A retreat or withdrawal (or retirement), shyness/reticence (as in being reserved), or a small indentation/depression (a hollow).
試合中に攻撃をやめて引っ込みを余儀なくされた。
They were forced to withdraw (retreat) and stop attacking during the match.
彼は引っ込み思案で、クラスの発表にはめったに出ない。
He is shy and rarely volunteers for class presentations.
道路の脇に小さな引っ込みができて、車が少し止められるようになった。
A small indentation was made at the side of the road so a car can pull over a bit.