amateur          
 adjective uk/ˈæm.ə.tər/ us/ˈæm.ə.tʃɚ/
C1 业余爱好的,非职业的
taking part in an activity for pleasure, not as a job
  an amateur astronomer/boxer/historian 业余天文学爱好者/拳击手/历史学爱好者 
 He was an amateur singer until the age of 40, when he turned professional. 40岁之前他一直是个业余歌手,之后才转为职业歌手。 
 Compare: professional adjective
  业余的;(尤指)业余体育运动的
relating to an activity, especially a sport, where the people taking part do not receive money
  amateur athletics 业余运动员 
 - More examples
 - The firm produces kits for amateur car constructors.
 - an amateur photographer
 - an amateur dramatic society
 - amateur theatricals
 - He's in charge of wardrobe at the local amateur theatre.
 
amateur          
noun [ C ] uk/ˈæm.ə.tər/ us/ˈæm.ə.t̬ʃɚ/
C1 业余爱好者;业余运动员
a person who takes part in an activity for pleasure, not as a job
  This tennis tournament is open to both amateurs and professionals. 这次网球锦标赛业余运动员和职业运动员都可以参加。 
 Compare: professional adjective
 C1 disapproving外行;粗通(某一行)的人 
someone who does not have much skill in what they do
  I won't be giving them any more work - they're a bunch of amateurs. 我有活也再不给他们干了,简直就是一帮外行。