To open out something that was rolled up into a tube or a ball, so that it lies flat. You unroll a yoga mat, a poster, a sleeping bag, a scroll of calligraphy, a roll of tape. It works both ways in grammar: you can unroll something (with an object), or something can unroll by itself — 'the map unrolled across the table'. That second use, with no object, is common and perfectly natural. The word carries a small sense of ceremony when the thing being unrolled is important — a scroll, a banner, a carpet — because unrolling reveals what was hidden inside. That is why 'roll out the red carpet' and its cousins feel grand. One honest note: for a poster stuck in a tube, English speakers will just as often say 'open it up' or 'flatten it out'. `Unroll` is precise and correct, but it is not the only or even always the most common thing people say. In writing, though, it is the exact word, and exact words are worth having.

攤開、展開（捲起來的東西）；把捲軸、地墊、海報打開鋪平。