ghostwriter       
noun [ C ] uk/ˈɡəʊstˌraɪ.tər/ us/ˈɡoʊstˌraɪ.t̬ɚ/
 幽灵写手; 代笔作家; 捉刀人
someone who writes a book or article, etc. for another person to publish under his or her own name
  He should have hired a ghostwriter to make his case. 他应该雇一个代笔将该说的说清楚。 
 The novel was largely written by an unacknowledged ghostwriter. 这部小说大部分是由一位不为人知的代笔作家写的。 
 See: ghostwrite
 - More examples
 - A growing number of professional ghostwriters are widely available.
 - The authors could not reveal their identities as ghostwriters.
 - It's not unusual for a prominent political figure to employ a ghostwriter for a memoir.