To slide is to move down or across something in a smooth way. If you’re into that kind of thing, head to a playground and go down a slide. Just don’t push any toddlers out of the way.
You can slide your bed across your room so it's near the window, or slide on the kitchen floor in your socks. You can also slide down a slide, a play structure that's designed for climbing up and sliding down. Another kind of slide is the small rectangular piece of glass that scientists slide under a microscope to examine specimens, or the photography slide you slide into a projector for viewing.