To trap, trick, or frame someone — to put someone into a difficult or compromising situation by deceit or stratagem.
彼はライバルを陥れるために偽の証拠を作った。
He fabricated false evidence to frame his rival.
あの政治家は敵を陥れる噂を流したと非難された。
That politician was accused of spreading rumors to discredit and trap opponents.
社員を陥れるような不正は決して許されない。
Unfair acts that trap or frame employees are never acceptable.
To capture or take (a castle, fortress, etc.); to reduce (an enemy stronghold).
軍は敵の要塞を陥れて領地を拡大した。
The army captured the enemy fortress and expanded its territory.
歴史書には多くの城が陥落する場面が描かれている。
Historical records describe many instances of castles being taken.
Originally: to drop something into (to let something fall into); often expressed as 落とし入れる.
彼は小さな手紙を箱の中に落とし入れた。
He dropped a small letter into the box.
釣り人は餌を桶に落とし入れて準備を整えた。
The angler dropped the bait into the bucket and prepared.