The city people mocked him as a hayseed because he didn't know how to use a smartphone.

hayseed 是由 hay（干草）和 seed（种子）组成的复合词，字面意思是"干草种子"。在俚语中用来形容来自农村、行为举止土气的人，带有贬义色彩，相当于中文的"乡巴佬"或"土包子"。