Up the Dictionary, Thesaurus and Wikipedia

We described earlier how tapping with three fingers while the cursor is over a word will look up that word in the Dictionary, Thesaurus and Wikipedia. If you don't have a trackpad or Magic Mouse, however, you can press ç+ß+D while the cursor is over a word (in some cases, such as words with apostrophe-denoted abbreviations such as ‘don’t’, you may have to select the whole word) to display its definition, synonyms and Wikipedia entry.