1) Four-party 2) Four-sided 3) Having many parts or sides 4) Having several or many sides 5) Many-sided 6) Multipartite 7) Quadrilateral 8) Quadripartite 9) Tetramerous 10) Three-cornered 11) Three-party 12) Three-sided 13) Three-way 14) Triangular 15) Trilateral 16) Tripartite Found on https://www.crosswordclues.com/clue/multilateral
having several or many sides; many-sided. · participated in by more than two nations, parties, etc.; multipartite: multilateral agreements on disarmament. Found on https://www.infoplease.com/dictionary/multilateral