Definition of raie ultime in US English:

raie ultime

noun

Physics
  • An emission line in the spectrum of an element which is the last (or one of the last) to remain detectable as the concentration of that element decreases.

Origin

1920s. From French raie ultime from raie line, stripe, band (in a spectrum) + ultime ultimate, last.

Pronunciation

raie ultime

/ˌreɪ ʊlˈtiːm/