1To feel down, sad, or depressed; to be in low spirits.
試験に落ちて、彼は一週間落ち込んでいた。
He was down for a week after failing the exam.
彼女は最近仕事でミスが続いて落ち込んでいる。
She has been feeling down lately because of repeated mistakes at work.
友達が励ましてくれて、少し落ち込みが和らいだ。
A friend's encouragement eased my low spirits a bit.
2To slump or deteriorate (e.g., business, economy) — to be in an unfavorable condition.
冬場は売上が落ち込むことが多い。
Sales often slump in the winter season.
景気が落ち込んで失業率が上がった。
The economy slumped and the unemployment rate rose.
3To fall into something (e.g., a hole) — a physical act of falling downward.
工事中の穴に足を踏み外して落ち込んだ。
I missed my step and fell into a construction hole.