In a couchant manner; in a reclining or lying down position.
From couchant (lying down) + -ly (adverb suffix), creating an adverb form to describe actions done while in a reclining state.
This word is rarely used outside heraldic descriptions because modern English usually just says 'lying down,' but in the formal world of coat-of-arms descriptions, 'couchantly' appears in official documents to describe exactly how that lion sits.
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