Adobe ACROBAT READER 7.0 Manual page 244

Checking the meaning of words in a Digital Edition
You can check the meaning of words on the Internet.
To check the meaning of words:
1. Use the Select tool
2. Right-click (Windows) or Control-click (Mac OS) the word, and choose Look Up
[selected word].
Your browser starts automatically and opens Dictionary.com (English only), and the
selected word or phrase is checked.
to select the word or phrase you want to check.