A Pap smear, also called a Pap test, is a screening procedure for cervical cancer. It tests for the presence of precancerous or cancerous cells on the cervix. The cervix is the opening of the uterus. A screening test for cervical cancer based on the examination of cells under the microscope. The cells are collected from the cervix, smeared on a slide and specially stained to reveal premalignant (before cancer) and malignant (cancer) changes as well as changes due to noncancerous conditions such as inflammation from infections. Also called a Pap smear.