this sentence is used as a extreme level of Deadass, this goes beyond just saying "on a stack" which means extremely decades, " on a Stack no lack" means your are very deadass to the point where there is no lack in your deadass.
example:
friend 1 : your girl cheated on you with me.
friend 2 : your joking ..haha
friend 1 : no am for real on a stack.
friend 2 : cant be .
friend 1 : am on a stack no lack.
friend 2 murders friend 1, no doubts.
Stupid ass teacher who happens to be short, fat, and a bitch.
Wow, she is worse than Bozena Lack-Bartley.
bitch ass teacher who don't know how to speak English.
To be a conscientious individual; always vigilant
Yo bruh, no lacking.
Jack Liss. president of the US after Kobe dies.
Ben: jack, wanna bang?
Jack: i would, but I lack jizz!
Am always with the strapped
Am always with the gang and those who will protect me
‘Said am never lacking’ was pop smoke’s anthem