Definition of jam up:
(n) :
an
outdoor place acting as temporary
accommodation in tents or other temporary structures; an organised event, often taking place in tents or temporary accommodation
(v) :
to live in a
tent or similar temporary accommodation; to stay in an advantageous location in a
first-person shooter game, for example, next to a power-up or to guard an area
"we're planning to camp in the field until Sunday."