The formation of a cleft lip or cleft palate.(noun)
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Use "clefting" in a sentence
"Oral clefting occurs when the tissues of the lip or palate of a foetus do not grow together early in pregnancy, and is a relatively common birth defect."
"Of course, the Japanese culture and language evolved together, through one another, as languages always do, and so if you have any familiarity with Japanese culture you may be note that this "clefting" structure is common mostly due to cultural factors."
"A clefting abnormality in vertebrae (small bones that make up the spine) that gives them a "flying butterfly" appearance on X-rays."