Keep
Keep verb - To mark with an appropriate practice, rite, or ceremony.
Open up
Open up verb - Cause to open or to become open.
Keep is an antonym for open up in topics: communicate, confess, let go, make aware, discharge a projectile.
Both terms in one sentence
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Ophelia's going to keep her lock to herself, not open up her chaste treasure to Hamlet's unmastered importunity, while Laertes will keep his key to himself.
Source: Theatre / Hamlet - Final Fantasy: The 4 Heroes of Light: Once you open up the Very Definitely Final Dungeon, monsters and bosses will keep pace with the party's levels.
Source: Dynamic Difficulty -
This doesn't explain why nobody cares when you open up their ancient heirlooms and keep the contents, though...
Source: Inexplicable Treasure Chests
Cite this Source
Open up and Keep. (2016). Retrieved 2026, August 16, from https://thesaurus.plus/related/keep/open_up
Keep & Open up. N.p., 2016. Web. 16 Aug. 2026. <https://thesaurus.plus/related/keep/open_up>.
Open up or Keep. 2016. Accessed August 16, 2026. https://thesaurus.plus/related/keep/open_up.
Google Ngram Viewer shows how "keep" and "open up" have occurred on timeline