1) To die of an overdose of drugs, typcially heroin.
2) In the tech industry, when karma pays back a system administrator (sysadmin) who generally thinks they are a computer god, by royally screwing up a computer with a simple task or software installation.
1) Jim Bo was a heavy user of heroin and he finally got godsmacked.
2) Charlie in IT operations installed an encryption program for us without reading the instructions as usual. He immediately was godsmacked when he rebooted and had to rebuild the whole system.