Told in Donnie Darko, my favorite word is 'cellar' and my favorite phrase is 'cellar door', according to the film, it's the most beautiful combination of words in the English language. I happen to agree.
It violates all the magical impulses of balanced onomatopoeic language - it of course means "beautiful", but its meaning is nothing of the sort, being stuffed to the brim with a brutally latinate cudgel of barbaric consonants.