Thievishly is an adverb that describes someone or something that is sneaky or inclined to steal. There are several synonyms that can be used in place of thievishly. Some of the most common ones include dishonestly, deceptively, unscrupulously, fraudulently, cunningly, and surreptitiously. Other possible synonyms include craftily, clandestinely, and underhandedly. Each of these synonyms conveys a slightly different shade of meaning, but all suggest behavior that is sly, shifty, or dishonest. When searching for synonyms for thievishly, it is important to consider the context and tone of the sentence in order to choose the most appropriate word.