What is XCOM second wave?

Related questions

1. Can I run XCOM Enemy Unknown?
2. What are Advent burgers made of?
3. What type of game is XCOM 2?
4. Does XCOM Enemy Within include Enemy Unknown?
5. Will there be more XCOM 2 DLC?
6. Can I run XCOM 2?
7. What does Advent stand for XCOM?
8. Do you need XCOM Enemy Unknown to play XCOM Enemy Within?
9. Is XCOM Enemy Within standalone?
10. Is XCOM 2 harder than Enemy Unknown?

Tags

1. #patch
2. #advanced
3. #enemy
4. #unlocked
5. #options
6. #randomness
7. #player
8. #released
9. #described
10. #below
11. #unknown
12. #enabled
13. #levels
14. #fourth
15. #second
16. #increase
17. #difficulty
18. #gameplay