Aptitude Test
As you probably know, aptitude refers to a person's capacity to learn. It should come as no surprise then that an aptitude test is a test designed to predict learning capacity for a particular area or particular skills. For example, the SAT is a test designed to predict how well you will perform in college (I won't get into the good and/or bad of this test). It is not designed to measure how will you did in high school (that would be an achievement test) but how capable you are of learning all the new skills necessary to do well in college.