put upside down or in the opposite position, order, or arrangement : invert the mousse onto a serving plate. invertebrate |ɪnˈvəːtɪbrət| noun an animal lacking a backbone, such as an arthropod, mollusk, annelid, coelenterate, etc. The invertebrates constitute an artificial division of the animal kingdom, comprising 95 percent of animal species and about 30 different phyla. Compare with vertebrate . give strength or energy to : the shower had invigorated her | [as adj. ] ( invigorating) a brisk, invigorating walk. See note at quicken .