two-dimensional
adjective uk/ˌtuː.daɪˈmen.ʃən.əl/ us/ˌtuː.daɪˈmen.ʃən.əl/
(SHAPE)
二维的，平面的
flat, having width and length but not depth
(TOO SIMPLE)
disapproving（人或故事）无深度的，肤浅的，浅薄的
A person or story that is two-dimensional is too simple, showing little deep, serious thought, or understanding
I didn't believe in any of the characters in the book - they were somehow two-dimensional. 我不相信书中的任何人物——他们被刻画得都有点肤浅。