snake oil
noun /ˈsneɪk ɔɪl/
  /ˈsneɪk ɔɪl/
[uncountable] (especially North American English, informal)- something, for example medicine, that somebody tries to sell you, but that is not effective or useful推销者的所谓 “万应灵药”;狗皮膏药(毫无用处或效果的推销品) - a snake oil salesman劣质品推销员 
 
- a snake oil salesman