名词
1. (狮子、狐狸等野生动物的)兽穴，兽窝
A den is the home of certain types of wild animals such as lions or foxes.
2. (家里用来学习、工作或从事业余爱好的)书房，私室
Your den is a quiet room in your house where you can go to study, work, or carry on a hobby without being disturbed.
3. (通常指为了从事非法活动的)秘密聚集处，窝点，巢穴
A den is a secret place where people meet, usually for a dishonest purpose.
4. (某一不良行为或非法活动的猖獗)场所，渊薮
If you describe a place as a den of a particular type of bad or illegal behaviour, you mean that a lot of that type of behaviour goes on there.