slippery

Etymology

From Middle English slipperie, an extended form ( + -y) of Middle English slipper, sliper (“slippery”), from Old English slipor (“slippery”), from Proto-Germanic *slipraz (“smooth, slippery”), equivalent to slip + -er. Compare also Middle English slibbri, slubbri (“slippery”) borrowed from Middle Dutch or Middle Low German slibberich (“slippery”). Cognate with German schlüpfrig (“slippery”), Danish slibrig (“slippery”), Swedish slipprig (“slippery”).

adj

1. 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.
   Oily substances render things slippery.
   The screeching of brakes, the monotonous blare of motor horns, the clip-clip of shoes on slippery pavements, the rustling of wet mackintoshes were all part of the great metropolis. 1936, F.J. Thwaites, chapter XXII, in The Redemption, Sydney: H. John Edwards, published 1940, page 214
2. (figurative, by extension) Evasive; difficult to pin down.
   a slippery person
   a slippery promise
3. (obsolete) Liable to slip; not standing firm.
4. Unstable; changeable; inconstant.
5. (obsolete) Wanton; unchaste; loose in morals.