To splay is to spread out or widen. Peacocks splay their feathers when they want to show off. Basketball players splay their fingers around a basketball to get a better grip.
The word splay is often seen as splayed. If you collapse on your bed with your arms and legs stretched out, you are splayed out on the bed. Fingers, toes, arms, and legs can all splay. Something that has a splayed shape is called a splay, like an architectural detail around a window or door. Splay comes from the verb display, originally "unfurl, unfold, or spread out."