You can consult MacOS X internal dictionaries from Vim by this plugin.
NeoBundle 'modsound/macdict-vim.git'
$ cd ~/.vim/bundle/macdict.vim/autoload/
$ make
:MacDict
-> Search an argument word with Japanese-English dictionary.
:MacDictCWord
-> Search the word under the cursor with Japanese-English dictionary.
:MacDictEnglish
-> Search an argument word with American English Dictionary.
:MacDictThesaurus
-> Search an argument word with American English Thesaurus dictionary.
:MacDictFrench
-> Search an argument word with French Dictionary.
:MacDictGerman
-> Search an argument word with German Dictionary.
:MacDictClose
-> Close output buffer.
You can change layout and window size through global variable in your .vimrc.
let g:macdict_window_size = 'botright 8split'