senior  
 adjective uk/ˈsiː.ni.ər/ us/ˈsiː.njɚ/
  (HIGH RANK)         
 B2 级别高的
high or higher in rank
  senior management 高级管理层 
 a senior government minister 政府高级部长 
 She's senior to me, so I have to do what she tells me. 她是我的上级,所以我得听她的。 
 Compare: junior adjective (LOW RANK)
  比其他成员年长的;比其他成员更有经验的
older and more experienced than the other members of a team
  The Dragons head coach praised his senior players in the 23-16 win. 龙队主教练称赞队里老队员在这场23比16的胜仗中的表现。 
 - More examples
 - a senior government aide
 - Two senior officials have been entrusted with organizing the auction.
 - The president was flanked by senior ministers.
 - Criticism has been levelled at senior figures in the industry.
 - She's just been promoted to senior sales rep.
 
  (OLDER)         
B2 [ before noun ]年龄大一些的 
older
  The more senior students are given some extra responsibilities. 年纪大一些的学生负起了更多的责任。 
 Compare: junior noun (YOUNGER)
  (UK written abbreviation Snr); (US written abbreviation Sr.)(置于姓名后,表示同一家人中同名的两人中的年长者)老,大 
used after a man's name to refer to the older of two people in the same family who have the same name
  Hello, may I speak to Ken Griffey senior, please? 喂,请问老肯‧格里菲在吗? 
 - More examples
 - This is the common room for senior pupils at the school.
 - I'm hoping to speak to Al Jackson, senior.
 
Idiom  
have a senior momentidiom  informal(就像老年人那样)忘记(某事) 
to forget something in a way that is thought to be typical of people who are old
 senior  
noun uk/ˈsiː.ni.ər/ us/ˈsiː.njɚ/
  (HIGH RANK)      
  [ C ]上级;上司 
someone who is high or higher in rank
  It's important to impress your seniors if you want to be promoted. 如果你想得到晋升,给你的上级留下好印象很重要。 
   (OLDER)          
20, 30, etc. years someone's senior 比…年长20/30岁等的
20, 30, etc. years older than someone
  She married a man 20 years her senior. 她嫁给了一个比她年长20岁的男人。 
 She's my senior by three years (= she is three years older than me). 她比我大3岁。 
  [ C ] US (UK senior citizen)年纪大的人 
an old person
  Seniors are entitled to a reduction of around 10%. 年迈人士可获10%降价优惠。 
  [ C ] US(中学或大学的)毕业班学生 
a student in their final year of high school or university