A shell is the command processor interface. The command processor is the program that executes operating system commands. The shell, therefore, is the part of the command processor that accepts commands. After verifying that the commands are valid, the shell sends them to another part of the command processor to be executed.
When Windows failed to boot, I needed to use a DOS shell.
Extreme intoxication through alcohol consumption. Typically characterised by the inability to respond coherently to even simple questions. Derived from 'shell of a man'. One step up the scale of drunkenness from battered.
That was an excellent night. There was loads of beer and I pushed through battered to achieve shell.