physically or mentally ill a sick child Her mother's very sick. Peter has been off sick (= away from work because he is ill) for two weeks. Emma has just called in sick (= telephoned to say she will not be coming to work because she is ill). (British English) Britain's workers went sick (= did not go to work because they were ill) for a record number of days last year. (North American English) I can't afford to get sick (= become ill).