IEEE, pronounced “Eye-triple-E”, stands for the Institute of Electrical and Electronics Engineers. The association is chartered under this name and it is the full legal name.
IEEE, an association dedicated to advancing innovation and technological excellence for the benefit of humanity, is the world’s largest technical professional society. It is designed to serve professionals involved in all aspects of the electrical, electronic and computing fields and related areas of science and technology that underlie modern civilization.
Source: https://supportcenter.ieee.org/app/answers/detail/a_id/190/~/what-is-ieee%3F