Without a cover or lacking any protective covering on top.
From 'cover' (Old French 'covrir' from Latin 'cooperire' meaning to cover completely) plus the suffix '-less' (Old English 'leas' meaning without or lacking).
The suffix '-less' is one of the most productive word-formation tools in English, meaning you can add it to almost any noun to create its opposite—like 'homeless,' 'fearless,' or 'wireless.' This flexibility is why English speakers can instantly understand 'coverless' even if they've never heard it before!
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