The term "twopenny-halfpenny" is a slang expression that means something is of low quality, insignificant, or cheap. Antonyms for this phrase include words such as admirable, excellent, first-class, high-grade, top-notch, and valuable. These antonyms express the opposite meaning of "twopenny-halfpenny" and convey a sense of excellence, value, and prestige. For instance, while "twopenny-halfpenny" implies worthlessness or insubstantiality, "excellent" suggests something that is of outstanding quality, superiority, and distinction. Therefore, by using antonyms, one can create a more nuanced and precise language to express the idea of value or worth of something.