If your snowman puts aside his heavy parka in favor of an undershirt, a turtleneck, a sweater, and a windbreaker, he's opted for clothing that's layered, which means "having one layer over another."
The root of the word layered — layer — probably came from the Middle English word describing brick layers, who spend their days, as the name suggests, laying bricks or making layered brick walls. It's not just bricks and clothing that get layered, of course: We often use this adjective to describe hairstyles and fancy recipes. What's one of the most useful qualities of bark, plywood, and even our own skin? They're layered.