The words that have opposite meanings to "corks up" include uncorked, opened, liberated, and released. Uncorked is the most direct antonym, as it means to remove a cork from a bottle. Opened is also an antonym because it suggests something has been unsealed, unfastened, or unpacked. Liberated and released are more abstract antonyms, but they imply that something has been freed or unburdened. All of these words suggest a sense of expansion, release, or lightness that is opposed to the restrictive, cramped feeling of being "corked up." Using the right antonym can help to clarify your meaning and convey a more nuanced expression.