When something is already bad, and you make it worse, you exacerbate it. A late night can exacerbate a cold. Fighting in front of the children can exacerbate a family problem. Doctors and news writers use this word a lot: smoke exacerbates asthma; skipped medicine can exacerbate an illness; a harsh comment can exacerbate a quarrel. It is a fairly formal, careful word. In everyday talk people more often say make worse. You exacerbate a situation, a problem, a feeling, or an illness — not usually a person. If you want the person-word, that is more like annoy or provoke. Though actually, the Latin underneath is about making something bitter and harsh, so the old picture is “make it sting more,” not just “add more of it.”