What does skimming mean with growing cannabis?

[Rocky Balboa]

I have heard this word used with cannabis before but what does it mean? Anyone know.

 

[Racefan]

as in skimming off the top? It could mean you need to skim foam or remove foam from the top of a reservoir or maybe the dealer was skimming a gram off every 8th.

 

[Rocky Balboa]

Oh ok.