Final answer:
The colloid osmotic pressure is the osmotic pressure exerted by plasma proteins in the blood vessels, which helps to reabsorb fluid from the interstitial space.
Step-by-step explanation:
The colloid osmotic pressure is best defined as the osmotic pressure exerted by plasma proteins in the blood vessels. In the capillaries, the plasma proteins create a concentration gradient that draws water back into the capillaries, helping to reabsorb fluid from the interstitial space. This pressure is also referred to as the blood colloidal osmotic pressure (BCOP) and plays a vital role in maintaining the balance of fluids between the blood and the tissues.