Snidely is an adverb that refers to something done in a sneaky, derogatory, or sarcastic manner. Some synonyms for 'snidely' include condescendingly, sarcastically, contemptuously, haughtily, derisively, and sardonically. These adverbs share the same connotation as snidely and are an excellent way to replace the word in a sentence. For instance, one could say, "he condescendingly remarked about my attire" instead of "he snidely commented on my outfit." Depending on the context of the sentence, choosing the appropriate synonym will add depth to the meaning and enhance the text's overall effect.