i Register
In some senses, sleek is marked as dated, colloquial. Watch for register when choosing this word.
adj
Having an even, smooth surface; smooth
sleek hair
So sleek her skin, so faultless was her make.
Glossy.
Not rough or harsh.
Those rugged names to our like mouths grow sleek.
Slim and streamlined; not plump, thick, or stocky.
But if it were like a rabbit that Rosa went, she came back like a weasel or some such sleek and lissom creature.
Healthy, well-fed and well-groomed; in good condition.
adv
With ease and dexterity.
verb
To make smooth or glossy; to polish.
The sloping brush sleeks the surface.
To calm or soothe.
To glide.