What is "dentable"

a. 1 Capable of being dented. 2 (context mathematics of a closed convex subset C of a Banach space Y English) Admitting slices of arbitrarily small diameter, where a slice of C is a subset of the form $S(lambda,alpha)$ = $\{yin\; C;|;\; lambda(y)geq\; ||lambda||\_\{infty,C\}\; -\; alpha\}$ for some $lambdain\; Y^*$ and some $alpha>0$.