com·press·ibil·i·ty \kəmˌpresəˈbiləd.ē, -ətē, -i\noun (-es) 1.: capability of compression < the compressibility of a fluid > 2.alsocompressibility coefficientorcompressibility modulus: a number expressing the change in volume of a gas, liquid, or solid per unit pressure and being the reciprocal of the bulk modulus