Uvular Rhotics
The uvular trill is used in certain dialects (especially those associated with European capitals) of French, German, Dutch, Portuguese, Danish, Swedish and Norwegian, as well as sometimes in Modern Hebrew, for the rhotic phoneme. In many of these it has a uvular fricative (either voiced or voiceless ) as an allophone when it follows one of the voiceless stops /p/, /t/, or /k/ at the end of a word, as in the French example maître, or even a uvular approximant.
As with most trills, uvular trills are often reduced to a single contact, especially between vowels.
Unlike other uvular consonants, the uvular trill is articulated without a retraction of the tongue, and therefore doesn't lower neighboring high vowels the way uvular stops commonly do.
Several other languages, including Inuktitut, Abkhaz, Uyghur and some varieties of Arabic, have a voiced uvular fricative but do not treat it as a rhotic consonant.
In Lakhota the uvular trill is an allophone of the voiced uvular fricative before /i/.
Read more about this topic: Uvular Consonants