shrivel
To become smaller, wrinkled, and dried out.
When something shrivels, it becomes smaller, wrinkled, and dried out. A grape left in the sun will shrivel into a raisin. A balloon slowly loses air and shrivels up. Leaves that fall from trees in autumn often shrivel and crunch under your feet.
The word usually describes what happens when something loses moisture or substance. Your fingers might shrivel after swimming for too long, getting all wrinkly and pruned. Plants shrivel when they don't get enough water, their leaves curling up and turning crispy. An apple forgotten in the back of your desk drawer will gradually shrivel, its skin puckering and folding.
You can also use shrivel to describe confidence or courage disappearing. Someone might say their courage shriveled before giving a big presentation, or that criticism made them want to shrivel up and disappear. When used this way, shrivel captures that feeling of wanting to become smaller and less noticeable, like a plant wilting in harsh conditions.
The opposite of shriveling would be plumping up, expanding, or flourishing: fresh, full, and alive rather than dried and diminished.