A few summers ago I analyzed over 60 past SATs and PSATs to find the top vocabulary words. We call them "Repeat Offenders." Since I can't give you the website with the definitions, I decided to just post the words here. They are too valuable not to share.
The numbers below show the percentage of tests that contained each individual word or a form of that word. For example, 49% of tests had a form of aesthetic, such as aesthete, aesthetically, aesthetics, etc. I recommend discarding any word you know and defining the ones that you do not. There are many, many more but obviously they are less common---let me know if you want me to post them.