The word "unpack" means to open and remove the contents of a luggage or package. Its antonym, however, refers to the opposite operation- that is, to pack or put things into a container. This term can take on different forms depending on the context, but some common words that serve as antonyms for "unpack" include "pack", "stuff", "fill", "load", "stuff in", or "cram". These words can be useful when discussing travel, storage, or shipping, and they imply that items are being placed within a case, bag, or box, rather than being taken out of it.