Incompetent means that the cervix is not able to function properly. It generally means that the muscles of the cervix are too weak to hold a baby in the uterus throughout pregnancy. A stitch may be placed at the opening of the cervix to keep it together.
A cervix with the inability to remain closed throughout an entire pregnancy, a frequent cause of premature birth. ... (09 Oct 1997) ... 
A condition in which the cervix
Incompetent cervix: A cervix that is abnormally liable to dilate and so is not competent to keep the fetus up in the uterus and keep it from being spontaneously aborted (miscarried).
A weak cervix that opens prematurely during pregnancy due to the pressure of the growing fetus. The condition is a common cause of second trimester miscarriages, but can be treated with a cerclage. Synonym(s): Cervical Insufficiency Narrower term(s): Cerclage
[n] - (obstetrics) uterine cervix that becomes dilated before term and without labor often resulting in miscarriage or premature birth
an abnormally weak cervix, which widens prematurely during pregnancy as a result of the weight of a developing foetus; may result in a miscarriage 
noun (obstetrics) uterine cervix that becomes dilated before term and without labor often resulting in miscarriage or premature birth
Cervix that dilates painlessly, without contractions.
Cervix that dilates painlessly, without contractions.
A condition in which the cervix, under pressure from the growing uterus, opens too soon without contractions before a pregnancy has reached term. It can cause a miscarriage in the second trimester or preterm labor in the third. Incompetent cervix is often treated with a cerclage.