Scoundrelly is an adjective that describes someone who is dishonest, untrustworthy, and immoral. Some synonyms for scoundrelly include deceitful, crooked, unscrupulous, devious, treacherous, and villainous. These words all suggest someone who is unprincipled and willing to break the law or take advantage of others for personal gain. Other synonyms for scoundrelly might include slippery, shady, duplicitous, and disreputable. These words all convey a sense of shadiness or sneakiness that is characteristic of a scoundrel. Regardless of the word used, being called scoundrelly is not a compliment, and suggests a person who should not be trusted or relied upon.