Popularized in a Missy Elliott song by the same name, the phrase "What the dealio?" is equivalent to "What's the deal?" or "What is up with this situation?"

Pseudo-Spanish for "deal", used to lend an air of urban-chic to an otherwise urbane sentence.

"Popularized in a Missy Elliott song by the same name..."

Fucking tweens and 20 somethings need to stop applying retarded, wishful definitions to words that were around before their birth. "Dealio" was not popularized by missy elliot, as it has been used consistently 20+ years before her music career got off the ground.

Contraction of "deal" and "yo."

1. A word that is used everyday most likely, but a word like no other. It is the douchey way of saying "deal" in an attempt to seem cool or superior to the other lesser mortals who say it normally. One of the more recent additions to acts of douchebaggery, however, people use it because they are not aware of the way they appear to the others in their company.

2. The lyrics to the song by P!nk. "what's the dealio?"

to inquire what is going on

A common misspelling of the term "dilly, yo".