unset
Unset a variable - the opposite of set. 
  
SYNTAX
      unset pattern	
e.g.
   unset name[subscript]    destroys the array element at index subscript.
   unset name               where name is an array, removes the entire array.       
unset removes all variables whose names match pattern, unless they are read-only.
`unset *' thus removes all variables unless they are read-only; this is a bad idea.
It is not an error for nothing to be unset.
"Look Dave, I can see you're really upset about this" - HAL (Space 2001)
Related commands:
  
  set - Set a variable
  unsetenv - unset an environment variable
  
  Equivalent BASH command:
  
  unset - unset a variable