Unauthorized collaboration is as the name implies, it's not allowed by the school unauthorized in other words, and it say collaborating or working with or helping another student or students with whatever the undertaking may be, be it collaborating with another student or students for purposes of an assignment, for purposes of an exam.
Unauthorized collaboration it does come up often in the college and university setting and even beyond say at the master's and PhD level and in law or medical school also. By the nature of the academic setting, students for better or worse can be tempted to engage in unauthorized collaboration and sometimes actually not even recognizing that they may be doing something improper.
It depends on the specific circumstances at hand, but there certainly will be instances where such collaboration a student would be well within his or her rights to do so. It does need to be considered in terms of the specific facts and circumstances at hand. It is a serious allegation. Having an experienced attorney advisor would be your best ally to help you understand and navigate the process and to help you take the best steps forward in an academic misconduct case.