slang Any hair product, especially oil or pomade, used to slick one's hair down and hold it in place. He had so much slickum in his hair that not even a tornado would have mussed it up! I hate running my fingers through his hair because they come out covered in slickum.
n. hair dressing, especially if thick and heavy. What kind of slickum do you have on your hair—bear grease? His hair was plastered down with slickum, and he looked like something in an old movie.