Synonyms for Convertible:

adj.

all (adjective)
exchangeable.
changeable (adjective)
flighty, changeful, flexible, reformable, mercurial, volatile, mutable, vacillating, unstable, Transposable, changeable, protean, irresolute, unsettled, fluid, precarious, versatile, shifting, alterable, modifiable, unsteady, varying, wavering, movable, fickle, exchangeable, adaptable, variable, transformable, ever-changing, inconstant, Vicissitudinous, adjustable, restless.
exchangeable (adjective)
transmutable.

n.

floating, brief, fleeting, short-term, transient, passing, short-lived, temporary. compact, automatic, cabriolet, estate, classic car, cruiser, demo, dragster. decimalize, basket, bureau de change, common currency, denominate, base currency, currency, change, decimalise. convertible (noun)
convertible security, cashable, transmutable, redeemable, exchangeable, sofa bed, adaptable, transformable, commutable, translatable.
interchangeable (noun)
equivalent, reciprocal.
vehicle (noun)
cart, bus, coupe, fire engine, buggy, gondola, roadster, taxicab, sled, wagon, sedan, auto, taxi, station wagon, jeep, barge, motorcycle, boat, car, ambulance, sledge, ferry, jalopy, motorcar, tractor, bicycle, brougham, stagecoach, truck, cab, conveyance, limousine, armored car, train, vehicle, boxcar, ship, van, automobile, landau, coach, hearse.

Other synonyms:

cabriolet, denominate, bureau de change, classic car, decimalize, currency, common currency. compact, cruiser. basket. demo. automatic, estate. change. Other relevant words:
convertible security, denominate, decimalize, cabriolet, sofa bed, passing, commutable, equivalent, exchangeable, demo, cruiser, dragster, automatic, transient, compact, translatable, basket, brief, short-term, floating, currency, change, reciprocal, transmutable, fleeting, decimalise, cashable, redeemable, temporary, estate, short-lived.