Look in the OED & you'll find "brrrr", with a rare 4 Rs: it's this one of the traditional 8 parts of speech
[DOC] [TLE] Free Flashcards about GRAMMAR/LIT TERMS - StudyStack [PAR] LOOK IN THE OED AND YOU'LL FIND "BRRRR" WITH A RARE 4 Rs; IT'S THIS 
ONE OF THE TRADITIONAL 8 PARTS OF SPEECH, INTERJECTION.