In a way that is in accord or agreement; harmoniously.
From accordant (adjective meaning in agreement) plus -ly (the adverb-forming suffix). This creates the adverbial form indicating an action done in harmonious agreement.
This adverb is rare but appears in formal or archaic writing when someone wants to describe doing something that fits naturally with something else—like 'proceeding accordantly with tradition.'
Complete word intelligence in one call. Free tier — 50 lookups/day.