Nonbilaterian is an umbrella term that collectively defines organisms lacking bilateral symmetry. Some common synonyms for nonbilaterian include radiata, radiate animals, and radially symmetrical. Radiata animals comprise a wide range of diverse groups, including cnidarians, ctenophores, and sponges. Other synonyms for nonbilaterian include asymmetrical, monoblastic, and diploblastic. Asymmetrical animals like sponges have irregular body shapes and lack any definite symmetry, while monoblastic and diploblastic animals have one or two embryonic germ layers, respectively. Synonyms for nonbilaterian organisms may vary depending on the specific taxonomic group, but the key defining characteristics remain the absence of bilateral symmetry and distinct body axes.