a deed or dealing: a weighty thing someone does, whether God's striking acts or a person's wanton practices
This word points to deeds that stand out, not routine activity. On God's side it names his memorable acts, the rescues and wonders his people retell and sing about. On the human side it usually names practices that invite judgment: a settled pattern of wrongdoing, not a single slip.
Because one word covers both, context does the sorting. In the songs of praise it carries the sense "make known what God has done"; in the prophets' warnings it carries the sense "your ways will catch up with you." The word itself does not say who acts or whether the deed is good; it simply marks the deed as significant.
In one narrow legal use it slides toward its darker edge. A husband who wants out of a marriage brings against his wife what the text calls, quite literally, a dealing built out of words: a set of trumped-up charges. Here the "deed" is a manufactured accusation.
A close cousin, מַעֲלָל, covers much of the same ground for human practices, while the ordinary word for any deed or thing made is מַעֲשֶׂה.