When you say 'closed source' do you mean that you can look at the source code, but it's not
open to share and change it - or do you mean that the source code is not public at all - or
the union of those two conditions (in other words anything that is not open source).
I think it would be better to avoid this term and if you want to say 'not open source', say
that. If you mean proprietary software, say that. If you mean software that has source code
available but is not open source... well, there's no good term for that and you have to be