To throw into (something); to dump or toss items into a container together.
ゴミ箱に紙を投げ入れたら、見事に入った。
I tossed the paper into the trash can and it went in perfectly.
材料をドラム缶に投げ入れて機械で混ぜる。
We throw the materials into the drum and mix them with a machine.
募金箱に小銭を投げ入れて、静かに去った。
He tossed coins into the donation box and left quietly.