1. Auxetic metamaterials are a type of metamaterial with a negative Poisson's ratio, so that axial elongation causes transversal elongation (in contrast to an ordinary material, where stretching in one direction causes compression in the other direction). (Wikipedia). 2. Auxetics designate a group of architectured materials that exhibit negative Poisson’s ratio. Such property implies that auxetics expand transversely when stretched, and shrink when compressed, contrary to conventional materials. (ScienceDirect, Additive Manufacturing Volume 47, November 2021, 102351).