/al"trooh iz'euhm/ , n.
1. the principle or practice of unselfish concern for or devotion to the welfare of others (opposed to egoism ).
2. Animal Behav. behavior by an animal that may be to its disadvantage but that benefits others of its kind, as a warning cry that reveals the location of the caller to a predator.
[ 1850-55; altruisme, equiv. to autru ( i ) others ( alterui, obl. form of L alter other ( > F autre ), with -ui from cui to whom; -l- restored from L alter ) + -isme -ISM; popularized through trans. of A. Comte, who perh. coined it, on the model of égoisme EGOISM ]