2-D

a.k.a. 2D, two-dimension, two-dimensional

Generally speaking, 2-D is anything of or having two dimensions, as height and width. Unlike 3-D, which is anything appearing to have depth or thickness in addition to height and width, 2-D is limited lacking substance or depth. Online slang includes having no depth, as in a two-dimensional character, for example "He was so boring, a total 2-D."