unselfishly concerned for or devoted to the welfare of others (opposed to egoistic).
2.
Animal Behavior. of or pertaining to behavior by an animal that may be to its disadvantage but that benefits others of its kind, often its close relatives.
Unselfish concern for the welfare of others; selflessness.
Zoology Instinctive behavior that is detrimental to the individual but favors the survival or spread of that individual's genes, as by benefiting its relatives.
[French altruisme, probably from Italian altrui, someone else, from Latin alter, other; see al-1 in Indo-European roots.] al'tru·ist n., al'tru·is'tic adj., al'tru·is'ti·cal·ly adv.