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.
yappology is a academic field concerned with the study on nonsense and cappolgy, subjects like gibberish, bullshitry and sophistry are studied in depth so that we can have no understanding of them at the end .
example of some who studies yappolgy *
yappologist : man is free when he is no cow
audience : he spoke nonsense! ð¥