Add the following to your .emacs file:
(require 'auto-dictionary)
(add-hook 'flyspell-mode-hook (lambda () (auto-dictionary-mode 1)))

Then just type.  When you stop for a few moments `auto-dictionary-mode' will
start evaluating the content.

You can also force a check using `adict-guess-dictionary', whether or not
`auto-dictionary-mode' is enabled.

If you're unhappy with the results, call `adict-change-dictionary' to
change it and stop automatic checks.

You can use `adict-change-dictionary-hook' to hook into any of these changes,
or `adict-conditional-insert' to insert text (like signatures) that will
automatically conform to the language.