immune organism immune organism that acts like it is not immune immuneButActsLikeNotImmune An immune organism that acts as if it is NOT immune (i.e., it seeks vaccination and/or avoids contact with infectious organisms). An organism of a particular species who is immune to infection with a pathogen of a particular species, and that acts as if it is NOT immune (that is, it does seeks vaccination, avoids contact with infectious organisms, etc.) William R. Hogan