1. Describes a moment when you are trying to solve a problem, and are wracking your brain and when you find how simple the answer is, you marvel at your own stupidity
2. When you are talking and totally forget what you are talking about
Person 1: Yeah and then I went to....*blanks out*
Person 2: What happened?
Person 1: I totally forgot what I was saying, tard moment #1.
Person 2: ha ha ha