n.

1. 硬纸板，卡纸板[U]
   The box is made of cardboard.

   这箱子是硬板纸制的。

a.

1. 硬纸板制的；扁而硬的
   He put his books in a large cardboard box.

   他将书放入一个大硬板纸箱内。

2. 不真实的，不自然的；虚构的，老一套的
   The story has several cardboard characters.

   这个故事里有好几个虚构的人物。

n.

1. pasteboard or stiff paper.
2. [as modifier] (of a fictional character) lacking depth and realism:
   superficial, cardboard characters.