Sleek describes something smooth, shiny, and streamlined in appearance. A sleek sports car has smooth curves and a glossy finish that looks fast even when it's standing still. A seal's sleek fur helps it glide through water with barely a ripple.

The word implies elegant efficiency, like everything unnecessary has been stripped away. A sleek design removes clutter and complexity. Modern skyscrapers often have sleek glass exteriors, and new technology products tend toward sleek, minimal shapes.

Sleek can also describe how something moves. A cheetah running across the savanna moves in sleek, fluid motion, its body perfectly designed for speed. When you see something sleek, whether it's a yacht cutting through waves or a well-groomed horse, you're noticing how form and function work together beautifully.

People sometimes describe hair as sleek when it's smooth, shiny, and perfectly combed, lying flat without flyaway strands. The word almost always carries a positive sense: sleek things look polished, sophisticated, and impressively well-designed.