The term 'thickened part of skin' can be described by two crossword solutions: CALLUS (6 letters) and CALLOUS (7 letters). A CALLUS is a thickening of the skin that forms as a result of pressure or friction, usually on the hands or feet. Calluses are generally painless and can help protect the skin from further damage. A CALLOUS is similar to a CALLUS, but it is usually caused by repeated exposure to cold temperatures or harsh chemicals. Callouses are often found on the hands and feet, and they can be painful.