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So, I was written up in my residence hall (the letter stating that the residence director wanted to discuss the accusations with me). Although I was brought to a judicial meeting, there was no actual disciplinary action taken against me. Given this, am I still required to disclose when an application states "have you ever been subject to disciplinary action?"

You should disclose. It is unlikely to have much of an impact on your cycle. Not disclosing could bite you in the ass down the road.

Based on the facts shared in your post, yes, you were subject to disciplinary action. If the question asked whether you were found guilty or punished by a disciplinary committee, then the answer would change.