We found this definition for the disconcerting penalty on Rey Maualuga that set up Nebraska’s touchdown.
“Use of disconcerting acts or words prior to the snap to interfere with (opposing player’s) signals or movements.”
UPDATED: Here’s the official rule: “No player shall use words or signals that disconcert opponents when they are preparing to put the ball in play. No player may call defensive signals that simulate the sound or cadence of (or otherwise interfere with) offensive starting signals. An official shall sound his whistle immediately.”