4. Gabrielle: Listen, these contracts will be done in one week. And after that, I promise you I will tell her everything. Trust me. The money she'll make, it'll cushion the blow.
Serena: As long as it's not physical, then I... I guess I can live with it.

cushion the blow: cushion有“减缓冲击”的意思，结合它的本意“垫子”应该不难理解。blow就是打击，cushion the blow意思就是减缓这件事情给她的打击，减少伤害。
physical: 这里的意思是只要你们两个人没有肉体关系
I can live with it: 我还可以忍受

5. Chuck: She told you about our little run-in last night.
Nate: You told me you'd back off.

run-in: 偶遇
back off: 靠边站，不管这件事，和leave it alone很像，但是语气更加严厉。

6. Blair: I thought if I proved the North Caro liar was cheating with his ex, that would be it, but she fell for his business meeting excuse-- monkey business, more likely.
Chuck: With Serena and Poppy both fighting over the banana.
Blair: I'm really worried, Chuck. You know how Serena is. She gets in over her head. We need to expose this two-timer for what he is.

fall for: to be deceived or swindled by，对谎言深信不疑
monkey business: silly, mischievous, or deceitful acts or behavior. 骗人的把戏
get in: to become or cause to become involved 陷入
two-timer: to be unfaithful to (a spouse or lover), double-cross，辟腿的人，同时有两个女(男)朋友