The word "acerbly" is an adverb which means sourly, bitterly and harshly. There are several synonyms that can be used in place of this word based on the context in which it is being used. Some of the synonyms include acridly, astringently, caustically, cuttingly, harshly, sharply, tartly and sourly. When describing a sharp and bitter tone, one can use either of these synonyms to create a more descriptive statement. Whether writing an essay, a story or simply trying to capture a mood or tone, the use of these synonyms can make a writer's work more meaningful to the reader.