dabbrev-completion is an interactive autoloaded compiled Lisp function in `dabbrev.el'.

It is bound to C-M-/.

(dabbrev-completion &optional ARG)

Completion on current word.
Like M-/ but finds all expansions in the current buffer
and presents suggestions for completion.

With a prefix argument ARG, it searches all buffers accepted by the
function pointed out by `dabbrev-friend-buffer-function' to find the

If the prefix argument is 16 (which comes from C-u C-u),
then it searches *all* buffers.