Tough skin is a term used to describe the outer layer of an organism's body, which is usually composed of dead cells and provides protection from the environment. The crossword solutions for this term are 'RIND' and 'HIDE, ' both of which refer to the tough outer layer of an organism. RIND is a more general term that can be used to describe the tough outer layer of any organism, while HIDE specifically refers to the tough outer layer of animals.