Source : Webster's Revised Unabridged Dictionary (1913)

Sleek \Sleek\, a. [Compar. {Sleeker}; superl. {Sleekest}.] [OE.
   slik; akin to Icel. sl[=i]kr, and OE. sliken to glide, slide,
   G. schleichen, OHG. sl[=i]hhan, D. slik, slijk, mud, slime,
   and E. slink. Cf. {Slick}, {Slink}.]
   1. Having an even, smooth surface; smooth; hence, glossy; as,
      sleek hair. --Chaucer.

            So sleek her skin, so faultless was her make.
                                                  --Dryden.

   2. Not rough or harsh.

            Those rugged names to our like mouths grow sleek.
                                                  --Milton.