snake

a snake in the grass

someone who pretends to be your friend while secretly doing things to harm you. It's upsetting to learn that someone you once viewed as a good colleague is in fact a snake in the grass.

See also: grass

snake oil (American, informal)

advice or solutions to problems which are of no use. In my opinion, government measures for balancing the budget are just so much snake oil.

See also: oil

a snake-oil salesman (American, informal)

someone who tries to sell you something of no value. The American people are too easily deceived - the perfect target for any passing snake-oil salesman.