Throw up Definition 1 of 4Pro Tip 1/3Physical Discomfort Often indicates the person feels ill and needs to relieve their stomach. After the rollercoaster ride, she had to throw up. Pro Tip 2/3Sudden Sickness Describes a quick onset of sickness, not a gradual feeling. The bad oysters made him throw up suddenly. Pro Tip 3/3Not Polite Considered informal and somewhat crude, so avoid in polite conversation. She had to leave the table to throw up.