Open Radar

 
Summary:
The built-in dictionary application provides an incredibly useful shortcut Ctrl-Cmd-D to provide the definition of the selected word or a word pointed to by the cursor. However this shortcut is implemented in a non-standard way. It does not show up in the keyboard shortcuts preferences pane nor is any indiciation this shortcut is used provided anywhere I can detect in the system.

Steps to Reproduce:
1. Highlight a word and hit ctrl-cmd-D. Marvel at the beautiful dictionary definition provided
2. Open System Preferences -> Keyboard -> Keyboard Shortcuts -> Services and look for the Ctrl-Cmd-D  shortcut

Expected Results:
A service for providing the dictionary definition will appear in Services (or possibly another section)

Actual Results:
None to be found.  You'll note a "Look up in dictionary" service exists, but this is a much less useful shortcut as it requires opening of the Dictionary app by default. (However configuring the preference to Dictionary Contextual Menu will allow this services entry to replicate the above behaviour)

Regression:
None

Notes:
If you configure another service to make use of this Ctrl-Cmd-D  shortcut, it will replace this behaviour yet provide no indication of a keyboard shortcut conflict.  (If you create other conflicting combinations a yellow exclamation mark appears beside the shortcuts)

Additionally if you happen to assign a shortcut to a service that is contextually sensitive  Ctrl-Cmd-D. Your service will be invoked sometimes and other times the dictionary.