An abstract/emotional verb meaning to lie to someone. This phenomenon is actually very old going back to the year 1877 of the days of Horace Beard, Sr. In those days, Horace was the town drunk, and always tried to get a free shot of whiskey from the town bar by telling the bartender that he was getting paid the following week.
The tradition continues even to today, with many people bearding many other people.
Daniel: Hey man, I just installed anti-gravity plates on my truck.
Jason: Man, there's ain't no such thing as anti-gravity plates for civilians, or any other ones that humans might produce. Well, maybe the Japanese, but I'm sure you don't have your hands on any.
Daniel: Naw man, I got anti-gravity plates from my dad who got them from the army.
Jason: Daniel, I believe you to be Bearding me. Don'tcha be bearding me, biyah.