you tell em

The Sound of Wavesから今日取り上げるのは単語ではなく、極めて口語的な表現です。
"As decided at the last meeting, .... Fortunately, rat-catching can be done in any weather, and I don't believe the police will get after us even if we kill a few rats outside the sewers"
There was general laughter and shouts of "You tell 'em! You tell 'em!"
"you tell 'em" の意味、用法が辞書で分かるでしょうか？
・http://www.english-slang.com/: Used to agree with or encourage someone in what he is saying.: The drunk was arguing with the bartenders and a man cried, "You tell 'em!"
・Urban Dictionary: The phrase "You tell em" is one of many sarcastic remarks which can be used to abruptly end a conversation. If you do not feel like responding to a certain person or your laughing at a complete idiot/moron/goon throwing out a "You tell em" will shut them up or induce a very interesting response.
この手の表現を普通の辞書で調べるのは難しいのですが、インターネットを使うと何とか調べ ることが出来ますね。