double up phrasal verb ( see also ↑ double )
1 . ( also double over ) to suddenly bend over at the waist because you are laughing so much or are in pain:
Emilio doubled over, grabbing his leg.
be doubled up/over with laughter/pain etc
Both the girls were doubled up with laughter.
2 . to share something, especially a bedroom
double up with
You’ll have to double up with Susie while your aunt is here.