Meaning of “concrete” - Learner’s Dictionary

concrete

noun [ U ] uk us /ˈkɒŋkriːt/

B2 a hard substance that is used in building and is made by mixing sand, water, small stones, and cement (= grey powder that is mixed with water and becomes hard when it dries):

concrete blocks

(Definition of “concrete noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)