What is Iniquity?


Most of us are familiar with the words of the King James version in 2Thessalonians 2:7, For the mystery of iniquity doth already work. 

But do we understand what iniquity is here?  Or how it is recognized?

2 Thessalonians 2:7-8  Today might read like this

7 For the mystery of lawlessness [… the coming reign of lawlessness] is already at work (this man has been doing these things for years); [but it is restrained] only until he who now restrains it (those who oppose the lawlessness and wickedness of this mans deeds) is taken out of the way (cast off the land or leaves)8 Then the lawless one (against the ways of Gods holiness) will be revealed (his deeds will be made know clear to everyone)