A term that when prefixed to a statement does more damage than good. Its purpose is to state that you are about to tell the truth about something. However, If one has to use this statement, it can be concluded that when that same person does not use this statement then they are lying, because when they are telling the truth, they state that they are about to tell the truth by saying, "I’m not gonna lie..."
So this statement, in effect, when used, devalues any potential credibility one once had as an honest and truthful person when they are not using the statement.
It is synonymous with: to tell you the truth
, as a matter of fact
, in fact
I'm not gonna lie, she is looking fine.
I'm not gonna lie, this taste terrible.
I'm not gonna lie, you are really good at what you do.