Somewhat feeble or slightly weak; moderately lacking in strength.
From 'feeble' with the suffix '-ish,' which means 'somewhat' or 'rather' and comes from Old English '-isc,' originally indicating 'of or pertaining to' before it became a general marker of approximation.
The '-ish' suffix is wonderfully vague and colloquial—'reddish,' 'smallish,' 'feeblish' all suggest you're not quite committing to the full definition, which is why it became popular in casual English and rarely appears in formal writing.
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