book up
phr. v..phr. v.. to reserve all the available spaces or tickets for something so that nothing is left.
phr. v.. to reserve or engage all available places, appointments, or tickets in advance; typically used in the passive voice to indicate a lack of availability.
The hotel is completely booked up for the summer.
If you want a table at that new restaurant, you should call now because they book up weeks in advance.
The conference center was booked up months before the keynote speaker was even announced, reflecting the high demand for the event.
Most commonly used in the passive form 'be booked up' to describe a full schedule or lack of vacancy.
Focus on the particle 'up' as a marker of completion or 'fullness', similar to 'fill up' or 'eat up'.
The flight is booked out.The flight is booked up.While 'booked out' is common in Australian and sometimes British English, 'booked up' is the standard phrasal verb for total lack of availability in most contexts.