ul ‧ tra ‧ sound /ˈʌltrəsaʊnd/ BrE AmE noun
1 . [uncountable] sound that is too high for humans to hear
2 . [uncountable and countable] a medical process using this type of sound, that produces an image of something inside your body:
investigation of the liver by ultrasound
An ultrasound scan revealed that the baby was a boy.