ultra- /ʌltrə/ BrE AmE prefix
[ Language: Latin ; Origin: ultra 'beyond' , from ulter ; ⇨ ↑ ulterior ]
1 . extremely:
an ultra-modern building
He remained ultra-cautious.
an ultra-light jacket
2 . technical above and beyond something in a range:
ultrasound (=sound that is too high for humans to hear)
⇨ ↑ infra-