The time right before university exams in which students no longer have to attend classes. Generally about a week long.
To 'swot' is to cram or study intensively.
Swotvac is a 'vacation' in which students are expected to study for their end-semester exams.
This term is used mainly in the UK and Australia.
During swotvac, uni students all stay home and try to cram in a semester's worth of learning.