A slicker is a waterproof coat, usually made of smooth, shiny material like oiled cotton or rubber, designed to keep you dry in rain or wet conditions. Sailors, fishermen, and farmers traditionally wore slickers because they spent long hours working outdoors in all kinds of weather. The smooth surface lets water slide right off instead of soaking through.

You might see a bright yellow slicker on a fisherman heading out to sea, or picture a classic detective in an old movie wearing a dark slicker while investigating a case in the rain. Some people call them raincoats or rain slickers.

The word can also describe someone who's smooth-talking and overly slick in manner. A city slicker is someone from an urban area who might seem fancy or inexperienced to people in rural areas. This use of slicker isn't quite as friendly: it suggests someone might be more style than substance, or someone who talks a good game but hasn't proven themselves through hard work.