Noun has 2 senses

• ultrasound(n = noun.phenomenon) - very high frequency sound; used in ultrasonography;

Derived form adjective ultrasonic₁

• ultrasound(n = noun.act) echography, sonography, ultrasonography - using the reflections of high-frequency sound waves to construct an image of a body organ (a sonogram); commonly used to observe fetal growth or study bodily organs;