I was sitting outside my apartment, smoking a cigarette and drinking a cup of coffee. I was watching a couple of doves in a pecan tree. Then a squirrel jumped out of the tree onto the roof of the apartments across the street. The squirrel was running across the peak of the roof about midways of the building. I was facing almost directly south when I noticed a triangular shaped object just above and to the left of the squirrel, coming at me at a high rate of speed. It was like a blurry triangular shape with a fuzzy, medium brown outline. It appeared to be a perfect triangular shape with one point up. The color of the body of the object appeared transparent, as it seemed to change color to match the sky and the clouds as it went past. I would guess the cloud cover to be at an altitude of about 1200 to 1300 feet. The object was flying under the clouds. The total time elapsed from the time it caught my eye to when it was out of sight was 3 seconds. There was no sound, no emissions, nothing but the sight of the object flying by. The speed of the object startled me and caused me to catch and hold my breath. I have never seen anything like it before. I know it wasn't just a formation of birds or anything like that because it was a perfect geometric shape. It appeared to be flying faster than the jets that fly over at the University of Texas graduation ceremonies and the F4 jets I have seen at airshows. It was flying so fast that my eyes were only able to focus on it momentarily and that's when I noticed 3 lighter brownish fuzzy lines equidistantly spaced in the body of the object. I also noticed at that time when it was almost directly above me that it appeared to be an elongated triangular shape. The two sides of the triangle were approximately 3 times the length of the back. The only way I could try to estimate the size of the object was to raise my arm and hold my thumb and forefinger apart at about the size of the length of it in the sky. That was about 2 inches total length. Considering the height of the clouds and the length the object appeared to be as it flew under the clouds it might be possible to estimate its length. To me it seemed to be about 1/2 to 2/3 the length of an F4 fighter jet. It flew in a perfectly straight line with no weave or bobble. I mentioned this incident to a neighbor lady who said I ought to report it.