What is Concrete ?
Concrete is (adj) 1. made of cement and sand a concrete path 2. real, important He had no concrete proposals to offer. The police are sure he is guilty, but they have no concrete evidence against him. (noun) a mixture of cement and sand, used in building Concrete was invented by the Romans. The pavement is made of slabs of concrete.(verb) to concrete something over to cover an area with concrete We concreted over the patio.
source: Easier English, Student Dictionary Upper Intermediate Level