You don’t say what the error message is, but I’m guessing that this is because currently only univariate distributions are broadcastable (make univariate distributions broadcastable by simonbyrne · Pull Request #760 · JuliaStats/Distributions.jl · GitHub). The workaround is simply to wrap the distribution in a Ref (or a 1-component tuple), like:
pdf.(Ref(Norm_def), [x,y])