to throw (something) into; to toss or shove into (emphasizing a forceful or careless action)
ゴミ袋をゴミ箱に放り込んでおいた。
I tossed the garbage bag into the bin.
急いでバッグに本を放り込んで出かけた。
I quickly shoved the book into my bag and left.
彼は腹いせに手紙を燃えるゴミに放り込んだ。
He, in spite, threw the letter into the burnable trash.
to throw in (in sports); to perform a throw-in (e.g., in soccer) — also used in some games for putting a piece into play
サイドラインから選手がボールを放り込んだ。
A player threw the ball in from the sideline.
相手のミスを見て、すぐにボールを放り込む作戦だった。
The tactic was to quickly throw the ball in after the opponent's mistake.