speak with tongue in cheek直译过来就是：“面颊上带着微笑说”，这个短语的正确意思是：“说说而已，假心假意地说”。因此，当美国人说"They just speak with tongue in cheek."时，他/她要表达的意思就是:"They are just saying that."、"They just talk the talk."、"They just pay lip service."。
Benjamin: Why are you still looking so depressed since we will finish the project tomorrow?
Terry: They said they will perform agreement, but they just speak with tongue in cheek.
①How can you fall for it?
②It is the perfect expression of denial.
③You should be tactful in dealing with everything.
④Learn how to discern and develop true friends.
1. fall for 信以为真
It's even easier to see how self-employed people fall for this happiness killer.
Only a credulous person would fall for that old trick.
2. tactful adj. 圆滑的，老练的
If you complain to the boss, be tactful. Don't lose your head.
She get them to accept these change by tactful management.
3. discern vt.识别，辨别
It is often difficult to discern the truth of an event from a newspaper report.
You need a long series of data to be able to discern such a trend.