windowpane

noun

1. A piece of glass filling a window or a section of a window.
2. A fabric pattern of widely-spaced intersecting vertical and horizontal lines forming large squares.“As for patterns, solids are the most formal, followed by stripes, nailhead, and birdseye (tiny, frequent dots on a darker background; nailhead is smaller and squarer), pic-and-pic (tiny, staggered diagonal lines, like miniature staircases), herringbone, windowpane, houndstooth, and glen plaid.”
3. A gelatin base tab with LSD.“Another form is called a windowpane. Windowpanes are small thin squares of gelatin treated with LSD that look like little pieces of plastic.”