Yes, thanks ramesh75. I found out that it's actually a Canadian Dept of Transport certification that allows one to self inspect & pass one's own stuctural work. It's relativly new.
Thanks for your response Rikman. This term is being used in the context of hiring preferences for structures work. It says simply "S33 preferred". I have training & experience in AC structural repair & maintenance but this term baffles me. I may just come out & ask them but...