The crossword solution for the term CARB is SPUD, which stands for 'Starch Polysaccharide Utilization Deficiency'. This is a medical condition in which the body is unable to properly digest and absorb carbohydrates. It is caused by a deficiency of certain enzymes that are necessary for the digestion of carbohydrates. Symptoms of this condition include abdominal pain, bloating, gas, and diarrhea. Treatment typically involves dietary modifications and enzyme supplementation.