Be sick Definition 1 of 5Pro Tip 1/3Physical Discomfort Implies actual nausea, not just a minor stomachache. The roller coaster made me so sick. Pro Tip 2/3Expressing Empathy Used to show sympathy when someone feels nauseous. You're sick? That's terrible, can I help? Pro Tip 3/3Immediate Reaction Often used to describe a sudden need to vomit. He looked sick and ran to the bathroom.