If you look in a dictionary, it will tell you that dalle means “slab”. However, I can think of two colloquial phrases where this word has a completely different meaning.
The first one is avoir la dalle, which means avoir faim, i.e. “to be hungry”.
J’ai la dalle, on bouffe quand ?
I’ve got the munchies, when do we eat?
You can also say crever la dalle (as well as crever de faim or the non-colloquial mourir de faim, “to starve”) if you are very hungry.
Je crève la dalle et y a plus rien dans le frigo.
I’m starving and there’s nothing left in the fridge.
The other phrase is que dalle, which means “nothing”.
Je pige que dalle à la politique.
I understand jack shit about politics.
Note that unlike rien, que dalle does not come after a past participe: you would say J’ai rien compris but J’ai compris que dalle.
Listen to the examples: