adjective: : Of or related to charity; altruistic, contributed as charity. The obvious usage refers to eleemosynary institutions, eleemosynary activities, and the like. Aren't they paying you enough? Prove you deserve more by telling them that your work is not intended as an eleemosynary contribution. (If you say "charity work" they won't look up from the desk.) It is an isolated adjective with no corresponding noun or verb.
Etymology: Medieval Latin eleemosynarius "alms" which gave Late Latin eleemosyna. This word entered Old English where it was reduced to "ælmesse" and further to "almes" in Middle English. The Latin stem was borrowed from Greek eleemosyne "pity, alms" from eleos "pity, mercy."
Source: Your Dictionary