the GNU version of the Collaborative International Dictionary of English
n. One who practices or advocates strict conformity to law; in theology, one who holds to the law of works. See legal, 2 (a).
The Century Dictionary and Cyclopedia
n. One who practises or inculcates strict adherence to law; specifically, in theology, one who regards conformity to the law as the ground of salvation, or who is rigorous in exacting obedience to the letter of the law.
Word Usage
"I've also been called a legalist and accused of thinking myself better than others (the true definition of legalism is believing that I must do certain things in order to be/stayed saved - which I don't, and wearing dresses wouldn't be one of those things!)."