<p><strong>adjective</strong></p><ul><li>costing much; expensive; high in price: a costly emerald bracelet; costly medical care</li><li>Synonyms: high-priced, dear</li><li>resulting in great expense: The upkeep of such a large house is costly</li><li>resulting in great detriment: It was a costly mistake because no one ever trusted him again</li><li>of great value; very valuable; sumptuous, lavish, extravagant</li></ul>