The phrase "with bells and whistles" refers to something that is fully featured or even exaggerated in its design or presentation. Antonyms for this phrase could include: basic, simple, plain, limited, understated, and modest. These antonyms indicate a lack of extravagance or extra features. While "with bells and whistles" might indicate something showy or flashy, these antonyms suggest a more subdued approach. For example, a software program could be marketed as "with bells and whistles" for its rich feature set, but customers seeking a more minimalist experience might prefer a program that is simple and limited.