A person or agent that avails themselves of something; one who makes use of or takes advantage of something.
From 'avail' plus the agent suffix '-er,' which derives from Old English and creates nouns indicating someone who performs an action. The term is archaic and rarely used in modern English.
In medieval property law, 'availer' was a specific legal term for someone who had the right to take advantage of land resources—it's a reminder that English legal terminology often fossilizes old words no longer used in everyday speech.
Complete word intelligence in one call. Free tier — 50 lookups/day.