An incident or accident when you collide with someone on the street who is too busy texting to look where they are going.
In the street when you are caught in the path of an oncoming Text Messager, you narrowly escape a Textident by jumping out of the way. Also screaming "Textident!" in their face at the last moment may save you, but 2 out of 3 texters are also wearing headphones and you will probably get mowed down anyway.
A textident is a specific, identifiable, unexpected, unusual and unintended external action which occurs in a particular time and place, without apparent or deliberate cause but with marked effects because of the act of texting. This is a negative probabilistic outcome which may have been avoided or prevented if you were not an idiot.