A deferral means that a student has not yet been accepted by their university. Deferrals are a common outcome among early-decision applicants. In this case, their applications will simply be reconsidered during the regular admissions period.
Waitlisting usually differs from deferral in that prospective students who are placed on a waitlist have reached the end of the admissions process and are likely not going to be reconsidered at a later date. Instead, the college has already decided that the student could be admitted, but only if some of its accepted students decide not to enroll.
