A certain amount/measurement of something that someone
will ask for. A shleb is relative and can
mean different amounts depending on the preferences, greed, and circumference of said
person.
Paddy: What do you want in your
tea?
Mary: Ah, just a shleb of milk!
Paddy: Grand so!
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Mary: What do you want on your toast?
Paddy: Oh just a shleb of butter will do there Mary!
Mary: Grand!