From Longman Dictionary of Contemporary Englishgroutgrout /ɡraʊt/ noun [uncountable] a mixture of sand, water and cement or lime that you spread between tiles when you fix them to a wall —grout verb [intransitive, transitive]
Examples from the Corpus
grout• In the bathroom, mildew had invaded the grout, and red towels hung over orange towels.• Always use waterproof grout on tiled worktops; ordinary grout will harbour germs.• After laying, the gaps between the individual mosaic pieces are filled with grout. 