Definition
to jointly use something, particularly a room, with another person
We need a double room since all the single rooms are booked, so we decided to double up.
When your friend comes to visit, you can share this room so you can double up.
On a family trip, due to accommodation costs, the parents decided to let the children double up.
to acquire or utilize twice the amount of something
Because the workload is heavy right now, we need to work overtime to double up our pay.
Their promotion allows customers to get double the product for the same price.
If you purchase this software now, you'll be able to double up your storage space.