The phrase "slippery sidewalks" means that the ground you walk on is very smooth and may cause you to lose your balance easily, making it hard to walk without falling. Full definition
I just want a black pair with a substantial heel for navigating slippery sidewalks that doesn't look dowdy. (bedknobsandbaubles.com)
«This winter, I had the opportunity to walk with a group that spent the entire time skating along slippery sidewalks and romping in snowdrifts. (educationworld.com)
We will help you recover for injuries caused by slippery sidewalks or floors, broken steps or stairways, or cracked pavement, asphalt or sidewalks (galyen.com)