The phrase "giving lowdown" implies providing information or details about a subject. Antonyms for this phrase could include "withholding information," or "keeping mum." Other antonyms might include "denying knowledge," "ignoring," or "concealing." The opposite of giving the lowdown could also be providing misinformation or false information. Synonyms for providing accurate information could include "informing," "enlightening," or "educating." Overall, the antonyms for "giving lowdown" emphasize the opposite actions or inactions related to sharing knowledge or insight.