Something that is slippery is smooth, wet, or oily and is therefore difficult to walk on or to hold.
The tiled floor was wet and slippery.
那磁砖地板又湿又滑。
You can describe someone as slippery if you think that they are dishonest in a clever way and cannot be trusted.
He is a slippery customer, and should be carefully watched.
他可是个狡猾的主顾,需小心提防。
slippery slope
If someone is on a slippery slope, they are involved in a course of action that is difficult to stop and that will eventually lead to failure or trouble.
The company started down the slippery slope of believing that they knew better than the customer.
该公司认为自己比客户更明白他们正在走下坡路。