Wiktionary
alt. (non-gloss definition: meaningless syllables used when humming a tune) interj. (non-gloss definition: meaningless syllables used when humming a tune)
WordNet
n. a set of nonsensical syllables used while humming a refrain [syn: tra-la]
Wikipedia
Tra-la-la is a song composed by George and Ira Gershwin for the 1922 Broadway show For Goodness' Sake. However, it was never performed in the show. It was later performed in the 1951 American film An American in Paris by Gene Kelly and Oscar Levant. In An American in Paris, it was listed as Tra-la-la (This Time It's Really Love).
Usage examples of "tra-la-la".
Keep the galaxy spinning, where would Candlepower be without the transmitter, tra-la-la.
If I dropped acid and went tripping tra-la-la across the rooftops and danced at the peak of the Statehouse dome, what would happen to him?
Like a young girl in whom the spring has awakened unidentified feelings, she began to sing tra-la-la with the spasmodic movements of the head that one would ordinarily expect of a guinea hen, knitting the while a new harness, which was to be flaming red.