Definition of ultra- in US English:

ultra-

prefix

  • 1Extreme; to an extreme degree.

    ‘ultramicroscopic’
    ‘ultraradical’
    extremely, exceedingly, excessively, immensely, especially, exceptionally, unusually, extraordinarily, remarkably, uncommonly, extra
    View synonyms
  • 2Beyond; on the other side of.

    ‘ultramontane’
    Often contrasted with cis-

Origin

From Latin ultra ‘beyond’.

Pronunciation

ultra-

/ˈəltrə//ˈəltrə/