Webster's Revised Unabridged Dictionary · 1913

Sleek

Sleek (slēk) , adjective

[Old English slik; akin to Icelandic slīkr, and Old English sliken to glide, slide, German schleichen, Old High German slīhhan, Dutch slik, slijk, mud, slime, and English slink. Compare 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

Sleek , adverb

With ease and dexterity. [Low]

Sleek , noun

1.
That which makes smooth; varnish. [Rare]
2.
A slick.

Sleek , transitive verb

To make even and smooth; to render smooth, soft, and glossy; to smooth over.
Sleeking her soft alluring locks. — Milton
Gentle, my lord, sleek o'er your rugged looks. — Shakespeare