Define global (all modes) abbrev for last word(s) before point.
The prefix argument specifies the number of words before point that form the
expansion; or zero means the region is the expansion.
A negative argument means to undefine the specified abbrev.
This command uses the minibuffer to read the abbreviation.
Don't use this function in a Lisp program; use `define-abbrev' instead.
(fn ARG)