Lacking health; sickly or in poor physical condition.
From 'health' (Old English 'hælth') plus '-less', a suffix meaning 'without' or 'lacking', creating a direct opposite of healthy.
The '-less' suffix is incredibly productive in English—we use it to flip adjectives into their opposites, and 'healthless' shows how speakers can create new words on the fly by just adding '-less' to almost anything!
Complete word intelligence in one call. Free tier — 50 lookups/day.