organizer          
noun [ C ] (UK usually organiser) uk/ˈɔː.ɡən.aɪ.zər/ us/ˈɔːr.ɡən.aɪ.zɚ/
B2 (竞赛,活动的)组织者;筹办者
the person or group who plans and arranges an event or activity
  There aren't enough seats for all the guests - I must tell the organizers. 来宾座位不够——我得告诉筹备人员。 
 Community organizers help to get people out to vote on election day. 社区组织者在投票日协助选民参加投票。 
  组织能力强的人
a person who is able to plan things carefully
  We need someone who is a good organizer. 我们需要一个组织能力很强的人。 
 - More examples
 - The fault lay with the organizers, who failed to make the necessary arrangements for dealing with so many people.
 - The organizers are forging ahead with a programme of public events.
 - To the mortification of the show's organizers, the top performers withdrew at the last minute.
 - The organizers say it's a fair contest but who knows what goes on backstage?
 - Tournament organizers need to offer big money to attract the top players.