“Slippery” (rebaladizo, escurridizo) you may know.
A surface or road can be slippery, and an object or a fish can be slippery. Slope you may also know (cuesta, pendiente, falda). If a surface is slippery, it can cause mortals and vehicles to slide (to slide = resbalar).
There are two idioms (modismos) that use the words “slippery slope”. Examine these:
- The Spanish government is on a slippery slope with its tax proposals.
This means that the government is in trouble (in the opinión of the voters) and things may get worse. Perhaps in Spanish you would say “…está en terreno resbaladizo“.
- A mortal can be slippery, and therefore not to be trusted. The idiom is “as slippery as an eel“ (anguila). So a slippery person is untrustworthy (no confiable).
So, governments are sometimes on a slippery slope, heading for real trouble, and on a slippery slope or road you should drive or walk with care.