The term "up code" refers to adding more digits or characters to a code in order to make it more specific or detailed. Antonyms for up code could include "simplify," "abbreviate," "truncate," or "condense." These words all connote reducing or making something smaller. Synonyms for up code might include "expand," "elaborate," "augment," or "enlarge," which imply a need for more information or detail. In practice, antonyms for up code will depend on the context and specific goals of the coding project.