"Box up" is a phrasal verb that means to pack or put something into a box. Its antonyms include the phrasal verbs "unbox" and "unpack," which mean to take something out of a box. Other antonyms for "box up" include "scatter," "disperse," and "distribute," which refer to the act of separating or distributing objects, as opposed to grouping them together in a box. Additionally, "uncrate" and "unload" are also antonyms of "box up," which specifically refer to removing items from crates or containers, without necessarily putting them into a box.