To sleep outside at night, usually because one has no home or shelter. Primarily heard in UK, Australia. The government's aim is to have the number of people sleeping rough halved in five years' time. I slept rough for a couple of years after my house was repossessed. It's not something I would wish on anyone.
When people sleep rough, they sleep out of doors, usually because they have no home. It makes me so sad when I see young people begging or sleeping rough on the streets. Note: You can also say that someone lives rough. He looked like he'd been living rough for the last few days.