Computers, Laptops & Tablets Apple Mac OS X Built-In Dictionary and Thesaurus Find Definitions for Words Instantly By Heinz Tschabitscher Writer A former freelance contributor who has reviewed hundreds of email programs and services since 1997. our editorial process Heinz Tschabitscher Updated June 14, 2019 Jamie Grill / Getty Images Apple Macs iPad Tweet Share Email A dictionary is the language user's best friend, and a thesaurus is the dictionary's soul mate. As you read and write emails, would it not be nice to have at hand a dictionary to define words, guide pronunciation, and elucidate etymologies as well as a thesaurus to find the right word by way of synonyms and antonyms? Mac OS X comes with The New Oxford American Dictionary and The Oxford American Writer's Thesaurus built in. Mac OS X Mail makes accessing these powerful tools particularly easy. Access Dictionary and Thesaurus in Mac OS X Mail To instantly access dictionary and thesaurus in Mac OS X Mail: Place the mouse cursor over the desired word.Press Command-Ctrl-D (think define).You can also tap with three fingers on the trackpad (with Look up & data detectors enabled in Trackpad preferences).Go to the Dictionary tab if you see it at the bottom of the definition window.In Mail 2:To access the thesaurus, select Oxford Thesaurus from the Oxford Dictionary drop-down menu.To see derivatives, origins, and phrases, click More…. Look up Multiple Words in a Row in Mail 2 This shortcut to the dictionaries works both when you read and when you compose messages. To look up multiple words quickly, keep Command-Ctrl pressed as you move the mouse cursor over desired words (you can release the D key). The same keyboard combination also brings up definitions in many other Mac OS X applications like Safari.