Stacked the deck

I was wondering if somebosy knows if "stacked the deck" speaking about playing cards is an idiom, and what it means.

Yes.

stack the deck (mainly American)

to arrange something in a way that is not fair in order to achieve what you want. The manager stacked the deck in Joe's favor so he got the promotion.
See also: stack
Cambridge International Dictionary of Idioms © Cambridge University Press 1998
idioms.thefreedictionary.com/ deck

An IDIOM is an expression whose meaning can't be derived simply by hearing it, such as 'Kick the bucket.'" See more types of phrases at www.phrases.org.uk bulletin_board 21 messages 482.html