To smear means to spread or rub something messily across a surface. When you accidentally smear peanut butter across the counter while making a sandwich, you've spread it in a careless, uneven way. Artists sometimes deliberately smear charcoal or paint with their fingers to create soft, blended effects.

The word carries a sense of messiness: smearing isn't careful or precise. If you touch wet paint and then smear it across a wall, you've made an unintended mark. Kids might smear fingerprints on a clean window or smear mud on their clothes after playing outside.

Smear also has an important figurative meaning: to damage someone's reputation by spreading false or misleading information about them. If someone spreads untrue rumors to make you look bad, they're attempting to smear your reputation. Politicians sometimes accuse opponents of running smear campaigns when they feel attacked with dishonest accusations. This kind of smearing is serious because reputations, once damaged, can be hard to repair.

A smear can also be a noun: the messy mark itself, like a smear of jelly on your shirt, or an attempt to damage someone's character through dishonest attacks.