slink
To move quietly and sneakily so no one notices you.
To slink means to move in a quiet, sneaky way, usually because you feel guilty, embarrassed, or don't want to be noticed. When you've done something wrong and want to avoid attention, you might slink out of the room hoping no one sees you leave. A cat who knocked over a plant might slink away with its ears back and tail low.
The word captures a specific kind of movement: slow, smooth, and trying to be invisible. It's different from running away or walking confidently. When you slink, you're almost hugging the walls, making yourself small, moving carefully so you won't draw attention.
You might slink past your parents' room when you're supposed to be asleep, or slink to your seat after arriving late to class. Animals slink through shadows when hunting or when they're scared. The word itself even sounds like the movement it describes: quiet, slippery, and a little bit shameful.
Someone who has slunk away (the past tense of slink) left quietly without saying goodbye, probably because they felt awkward about the situation.