He alwyas kisses up to the boss.
kiss原意“亲吻”，本是表示喜爱的动作，可如果对着一张并不可爱的脸也一脸谄笑地要去kiss，甚至去kiss他的手，他的脚，那就一定是有求于人了。所以kiss up to sb. 这个短语的意思是：“奉承讨好，拍马屁，巴结”。因此，当美国人说:"He always kisses up to the boss."时，他/她要表达的意思就是"He likes to flatter his boss."、"He alwayssucks up to the boss."、"He seizes everyopportunity to curry favor with the boss."。
Toddy: Ben, I hear that the laziest guy in your company has been promoted. That's ridiculous!
Benjamin: Forget it! He always kisses up to the boss.
①How could he get a promotion so fast?
②Do you know that the newcomer has been appointed to department head?
③Everyone in our department dislikes him.
④He is always late for work but has never been blamed by the boss.
1. suck vt. 吮吸
They waited in silence and sucked their sweets.
Doran was clutching the bottle with both hands and sucking intently.
2. curry favor 拍马屁，巴结
You could argue he'd done it to curry favor with the guards.
He licked the dust in order to curry favor with the political boss.