mountain  
noun [ C ] uk/ˈmaʊn.tɪn/ us/ˈmaʊn.tən/
  (VERY LARGE HILL)      
 A2 (高)山,山岳
a raised part of the earth's surface, much larger than a hill, the top of which might be covered in snow
  The Matterhorn is one of the biggest mountains in Europe. 马特豪恩峰是欧洲最雄伟的山峰之一。 
 The Rockies are a mountain chain/range in the western United States. 落基山脉绵亘于美国西部。 
 I'd love to go mountain-climbing. 我想去爬山。 
 We're going to the mountains (= an area where there are mountains) for our holiday. 我们要去山区度假。 
 - More examples
 - We camped on one of the lower slopes of the mountain.
 - The view from the top of the mountain is breathtaking.
 - What's the highest mountain in Europe?
 - After three days lost in the mountains, all the climbers arrived home safe and sound.
 - They slowly ascended the steep path up the mountain.
 
  (LARGE AMOUNT)        
a mountain of somethingC2 大堆,大量
a large amount of something
  I've got a mountain of work to do. 我有大量的工作要做。 
 There was a mountain of paperwork to deal with.
 By this time, he had amassed a mountain of debt.
 All that was left of the apartment block was a mountain of rubble.
 We were stuck at the airport with mountain of luggage.
 The bridge was by now nothing more than a mountain of debris.
  UK(食品的)大量存库 
a large amount of food that is stored instead of being sold, so that prices for it do not fall
  a grain mountain 大量积压的谷物 
 Idiom   
make a mountain out of a molehillidiom  小题大做
to make a slight difficulty seem like a serious problem
  You're making a mountain out of a molehill. You wrote one bad essay - it doesn't mean you're going to fail. 你在小题大做——你一篇论文没有写好,但这并不意味着你就会不及格。