Inability to achieve closure of the velopharyngeal sphincter (closure of the muscle of the soft palate) during speech, owing to muscular dysfunction, cleft palate, or other disorders.
Note: This insufficiency often causes speech problems by allowing air to escape through the nose instead of the mouth.
Source:
PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 819 (https://doi.org/10.1515/pac-2015-1202)