Derived from the trend of planking, bating, and owling. Originated in Chicago, IL; it involves the opening of ones mouth, a surprised facial expression, and the deliverance of a guttural utterance while standing perfectly still. The sound that is made resembles that of a vocally challenged person moaning aggressively with a closed throat.
Bob: "Hey Jim, what are you doing?"

Jim: "Well, I'm just about to go to the store to get some milk and *wailing* AHHHHUUUUGHHHHAHHHHH!"
by TheJanitorialBatman February 22, 2012
verb.
To beat up someone using a flurry of punches and kicks thrown quickly one after another and landing so fast that the victim has no time to avoid or block any of them.
yo that big nigga's gonna wail on that lil nigga and fuck him up!
by ktpants July 11, 2008
To go nuts on any instrument, including the voice, by either playing extremely hard or hitting the money highnote.
The saxophonist from the 80's group Men at Work really wails throughout the song "Who Can It Be Now."
by Bunny D May 25, 2005
To weep loudly, to cry or bawl, to lament or mourn for someone.

To cry out, usually in grief.
The wind was howling outside that night. At about midnight, we heard a woman wailing, broken by occasional sobs. We knew instantly that it was the banshee. We knew then that one of us would soon die.

As I was locking up for the night, I heard a little girl somewhere in the building, and she was wailing. Following the sound into into the women's room, I saw a little girl of about four, her face flushed from crying. As I walked towards her, she disappeared. Was this my imagination or had I seen a ghost?
by Lorelili April 6, 2008
Amongst the purest and kindest human being that you’ll ever encounter. Such a gentleman with a beautiful smile that whenever you’ll look at their face, they’ll make your day a billion times brighter. Such a lovely person with a kind-heart. No matter when or wherever you need them, they’ll always be there for you. They’ll always have your back and can make your day go from 0 to 100. Wail, I love you!
F: Wail, you’re so cute!
W: Heyyy- no you are
by FAWFAA October 29, 2018
Often used to describe the extremely aggressive punching action of one person against another during a fight
Did you see that? He was wailing on that guy!
by Bungalow Bill October 18, 2001
To make an intensely high note on a guitar.
Nobody can out-wail Yngwie Malmsteen.
by Endril March 21, 2003