From Longman Dictionary of Contemporary Englishdouble as somebody/something phrasal verbUSE somethingto have a second use, job, or purpose as a particular thing The school doubled as a hospital during the war. → double→ See Verb table
Examples from the Corpus
double as • Preferably swathed in a scarf which can double as a belt, a bikini top - or even as a scarf.• Then they would sell them to posses from a garage on Bruckner Boulevard that doubled as a muffler repair shop.• Schools often double as daycare or healthcare facilities, or house adult classes and sports activities.• Columns of cast iron doubled as drainpipes and supports for the ceiling, which had domed skylights.• They still carried the ball, but the electors moved from being spectators to doubling as occasional umpires as well.• The serious ones turned out finely crafted, sensitive drawings of the dead that double as somber meditations on death.• The living room, doubling as the bedroom, was full of the odor of her sleep.• Grant engages in some lightweight banter with the radio controller, Mickey, who doubles as the Cutter Boat Club barman. 