Calicivirus: A group of viruses belonging to the family Caliciviridae that includes:

• Norovirus, a common cause of food poisoning and acute gastroenteritis in humans;
• Sapovirus, formerly called "Sapporo-like virus" (SLV) and sometimes referred to as classic or typical calicivirus, which can also cause gastroenteritis in humans;
• Vesivirus, the swine vesicular exanthema virus; and
• Lagovirus, the rabbit haemorrhagic disease virus.

The hepatitis E virus, once considered a calicivirus, now belongs to an unassigned (or floating) genus called the hepatitis E-like viruses.

All of the caliciviruses are single-stranded RNA, nonenveloped viruses. Their genetic information is encoded in a single strand of RNA and they lack an envelope. The name calicivirus comes from their characteristic "Star of David" shape with cup-shaped (chalice) indentations.