To descend to the level of someone else, usually in a way that shows you think you're better than them.
From Latin 'con-' (with) and 'descendere' (to descend). The meaning evolved to describe a superior person lowering themselves to interact with someone of lower status.
This word is basically the verb form of 'condescend,' but it's so rare that most dictionaries have largely abandoned it in favor of the more common adjective 'condescending'—a great example of how languages naturally select the most useful forms and let others fade away.
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