joiner  
noun [ C ] uk/ˈdʒɔɪ.nər/ us/ˈdʒɔɪ.nɚ/
  (WOOD WORKER)     
  木匠,木工
a skilled worker who makes the wooden structures inside buildings, such as doors and window frames
   (TAKING PART)         
 参与者;加入者
someone who agrees to take part in an arrangement or become a member of an organization
  Recent joiners are in a worse position than existing members. 最近的加入者比现有会员的处境要糟糕。 
  informal社团活跃分子 
a person who likes to get involved in activities with groups of people
  I don't think you'll persuade David to come along to tonight's meeting - he's not much of a joiner. 我认为你不可能说服大卫来参加今晚的会议——他可不是社团活跃分子。