Snap In physics, jounce or snap is the fourth derivative of the position vector with respect to time, with the first, second, and third derivatives being velocity, acceleration, and jerk, respectively; hence, the jounce is the rate of change of the jerk with respect to time. [Wikipedia: https://en.wikipedia.org/wiki/Jounce] Mechanics Aquarius ODM2 Units Type Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of the Unit or the more general quantity that the Unit represents.