From Longman Dictionary of Contemporary Englishnot to mention somethingnot to mention somethingAND/ALSOused to introduce an additional thing that makes a situation even more difficult, surprising, interesting etc Pollution has a negative effect on the health of everyone living in the city, not to mention the damage to the environment. It’s too far to walk, not to mention the fact that it’ll probably be closed by now anyway. → mention
Examples from the Corpus
not to mention something• Shaver said the culprit may face a prison sentence, not to mention a $ 3. 4 million firefighting bill.• Gary Lineker would have looked great in that, not to mention Gazza.• It has the support of the farmworkers' unions, not to mention soil technicians and mental-health professionals.• Catriona decided not to mention that she hated cigarette smoke.• Jack's father had asked him not to mention the accident in front of the younger children.• He decided not to mention the brooch.• Harrowing for the patient, not to mention the expense incurred. 