The Brief: No cap means "no lie."

DEEP DIVE
No cap is a synonym for TBH and signifies a moment of honesty. It is used to indicate speaking from the heart.
“Cappin” is also used to mean “lying,” especially in calling out someone else’s dishonesty.
The date of the album release is incredibly soon. No cap https://t.co/UXut2UKUfW
— Ari Lennox (@AriLennox) February 8, 2019
Does cappin give y’all an adrenaline rush or sum ? 😂
— s (@queenlilboat) February 7, 2019
it’s a lot of cappin going on but that don’t got nothing to do wit me
— CHANEL MURDER (@ChanelMurder) January 30, 2019