Picking and choosing the tenets of a religion that you would like to follow. Often choosing the convenient parts (the holidays and celebrations) and leaving the rest.
"Is Greg Jewish? He doesn't keep kosher."
"Yeah but he takes all of the holidays though."
"He must be practicing pick and choodiasm."
"You're eating meat? I thought Catholics abstained from meat on Fridays in Lent."
"No worries dude, I'm practicing pick and choodiasm."