A fork of Rural Dictionary
Derived from the great Paul Young, to be 'youngin it' is to switch from a relaxed and jovial mood, into a vitriolic fury. This switch is often performed in a swift or fast fashion, often unnoticeable until an outburst occurs.
Michael: "Have you heard about the Kodiak Bear?" Kathryn: "Michael ENOUGH!" Michael: "Wow, really youngin' it today, aren't you."