In a manner that shares common boundaries or has the same extent; in a way that is conterminous.
Adverbial form of 'conterminous,' adding the standard adverbial suffix '-ly' to the adjective to create an adverb describing how something shares boundaries.
Adverbs ending in '-ously' often make concepts abstract—'conterminously' turns a spatial relationship into a manner of being or describing, which is why it's so rare in modern English!
Complete word intelligence in one call. Free tier — 50 lookups/day.