When somebody cannot answer you in a real sentence, but instead merely mumbles something you can't quite hear, and trails off; possibly chuckling as they do so. It is an unexplained phenomena that usually occurs under stress, or if that person is not comfortable speaking with particular people and is trying to get away.
slip of the tongue perhaps,
Those idiots who drive around in a ridiculously raised pick up truck, making a top heavy vehicle even more top heavy and unstable
A:*gah*
B: "Whats the matter"
A: This dam prickup is blinding me.
B: Stupid thing's, as if there lights weren't blinding enough as it is.