Lubricious
Part of speech: adjective
Definition: smooth and glassy; slippery lewd, wanton, salacious or lecherous
Slippery
Part of speech: adjective
Definition: Of a surface, having low friction, often due to being covered in a non-viscous liquid, and therefore hard to grip, hard to stand on without falling, etc.Evasive; difficult to pin down.
Example sentence: Of all the arguments against voluntary euthanasia, the most influential is the 'slippery slope': once we allow doctors to kill patients, we will not be able to limit the killing to those who want to die.