"Up snuff" is an informal phrase that means "at an acceptable level of quality or performance." When looking for antonyms for this term, one could consider words like "substandard," "unacceptable," "inadequate," and "unsatisfactory." Other options might include "below par," "deficient," "inferior," and "lacking." Using these antonyms in place of "up snuff" would indicate that something falls short of expectations or standards. It's important to remember that context is key when selecting antonyms, as certain words might be more fitting depending on the situation.