Is the "Lookup in Dictionary" context menu option hardcoded in Google Chrome for Mac?
What you are seeing are the OSX built in Text Services, such as Spelling and auto-correct services when dealing with anything in OSX that is text.

These services are automatic for the whole OS and cannot be turned off and are available in every application

Note: Spelling Auto-Correct can be turned off/managed in System Preferences -> Languages &amp; Text -> Text

The "Services Manager" and the "Dictionary Service" only relate to what is shown and provided in the Services Menu within running applications.  you can turn off those within (oddly enough) System Preferences -> Keyboard -> Keyboard Shortcuts -> Services