Mucous/ˈmjuːkəs/ Definition 1 of 2Pro Tip 1/3Body Fluid Mucous is a specific type of bodily fluid, thicker than saliva. Her throat felt irritated by the mucous. Pro Tip 2/3Health Indicator Changes in mucous can indicate health problems like infections. The doctor checked the color of the mucous. Pro Tip 3/3Not Snot Don't confuse 'mucous' with 'snot'; 'snot' is less formal and specifically nasal. He assumed the mucous was just snot, but it was different.