In a manner that involves dictating or commanding; in the style of one who dictates.
From 'dictate' (Latin dictare) + '-ingly' (adverbial suffix). The '-ingly' suffix evolved from Old English '-inge' to form manner adverbs.
You might say a strict teacher speaks 'dictatingly' when they're constantly commanding rather than asking—it's the adverb form that describes a dominating communication style.
Complete word intelligence in one call. Free tier — 50 lookups/day.