Capable of being agreed upon or acceptable; agreeable.
From agree plus the suffix -able (meaning capable of being). This appears to be an archaic or dialectal variant of 'agreeable,' used historically to mean 'suitable' or 'willing to agree.'
This word is so rare that even most dictionaries don't include it, but it shows how English speakers in earlier centuries would creatively form new adjectives by adding -able to almost any verb!
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