nonhierarchical

:  not hierarchical; especially :  not divided into, organized by, or involving different levels of importance or status a nonhierarchical organization/structure All great groups have extraordinary leaders. It's a paradox, really, because great groups tend to be collegial and nonhierarchical, peopled by singularly competent individuals who often have an anti-authoritarian streak. — Warren Bennis and Patricia Ward Biederman