I wonder can poor general GRE exam hurt an application with very strong GPA (about 3.9) and good letter of recommendations for getting an admission to top graduate schools in US? meaning that How strong is effect of GRE ?can you be rejected based on your GRE result?
I am not in engineering, but chemistry, and I suspect the answer is very similar.
I won't lie. This will definitely hurt your chances, depending on how low your score is.
For one, many programs have minimum GRE scores for acceptance - that may or may not be advertised. There are so many highly qualified applicants to top schools that the admissions committee have to do something to cut back the pile. While there are advantages and disadvantages to the GRE, it is standardized and using a score level as a filter is helpful to the committee. (Usually this "first cut" is a GRE score well below the average admitted score. We know that some students don't test well, so we'd prefer to look at the whole package.)
Beyond "your score is too low," let's assume you make the first cut. At that point, the GRE matters less, since the committee will read your recommendation letters, look at your transcript etc.
Even then, the GRE matters some. If we're considering a student coming from a school that we don't know, we simply cannot calibrate the GPA and/or the recommendation letters. So the GRE gives us some information on what a 3.9 GPA "means" relative to another student at a school that we know.
Finally, the GRE is a piece of information to the admissions committee. One key thing it tells us is how seriously you took the exam and whether you prepared for it. We know that the GRE is a self-selecting bunch. You only take the exam if you're considering applying to graduate programs. So if someone gets a very low score.. well, that's not a good sign. What do we learn about how serious a student will be in grad school?
All that said, I have talked over the years with colleagues in other departments and other schools. There isn't a huge correlation between GRE scores and success in graduate school. There just isn't really anything better either.