We validate the Measure of Acceptance of the Theory of Evolution (MATE) on undergraduate students using the Rasch model and utilize the MATE to explore qualitatively how students express their acceptance of evolution. At least 24 studies have used the MATE, most with the assumption that it is unidimensional. However, we found that the MATE is best used as two separate dimensions. When used in this way, the MATE produces reliable (a > 0.85) measures for (i) acceptance of evolution facts and data and (ii) acceptance of the credibility of evolution and rejection of non-scientific ideas. Using k-means cluster analysis, we found students express their acceptance of evolution in five distinct profiles: (i) uniform high acceptance; (ii) uniform moderate acceptance; (iii) neutral acceptance; (iv) acceptance of facts, but rejection of credibility; and (v) rejection of both facts and credibility. Furthermore, we found that knowledge of macroevolution moderately explains students' acceptance profiles, corroborating previous claims that teaching macroevolution may be one way to improve students' acceptance. We use these findings to express the first set of operational definitions of evolution acceptance and propose that educators continue to explore additional ways to operationalize evolution acceptance.