A suppressant is something that holds back, reduces, or prevents something else from happening or appearing. The most common use is in medicine: a cough suppressant is a medicine that stops or reduces coughing, helping you rest when you're sick. An appetite suppressant reduces feelings of hunger.

Think of a suppressant as something that pushes down on whatever it's meant to control. Fire suppressants put out flames or keep them from spreading. Weed suppressants stop unwanted plants from growing in gardens.

You'll also hear about immune suppressants, which are medicines that intentionally reduce the body's immune response. This might sound strange (why would you want to suppress your immune system?), but doctors use them to help organ transplant patients, since the immune system might otherwise attack the new organ as a foreign object.

The key idea is that a suppressant doesn't eliminate something entirely; it reduces or controls it. A cough suppressant doesn't cure your cold, it just helps manage one symptom while your body heals.