1. to sleep for long periods of time (or to nap throughout the day) so as to gain more rest. It is useful when you know you will be experiencing sleep deprivation in the near future.
2. to add to your sleep credit so you can be awake longer periods of time.
3. "...you can banksleep in advance. Her study showed that people who built up a ‘credit’ of extra sleep by sleeping more every night for a week before being deprived of sleep suffered fewer ill effects of sleep deprivation (Claudia Hammond, BBC).
"John knew that he would be pulling an all nighter Thursday so he decided to bank sleep Wednesday."