What is Murumbling?
1.
When a person attempts to sing a song's lyrics but is only able to sing the more memorable parts and just mumbles the rest as part of the tune in a non-sensical fashion.
"comin' outta my cage and I've been doin' just fine, do-do-dododo dododo, it started out with a kiss how did it end up like this, it was only a kiss it was only a kiss"
"What was that?!"
"Just murumbling"
See