Masato: you can consult the system's built-in dictionaries
Not here, not under Yosemite. Probably because Igor stole the context menu.
Did you know you can add dictionaries to the Kamus.app? Apart from the built-in ones, that is.
I don't have a trackpad, and I checked the settings for the Magic Mouse, and it's not available. Besides, I think it's related to the context menu, and contrary to popular belief, CT isn't a particularly good Mac citizen: The OS X context menu isn't accessible in CT (among many other things).
Can you provide a screenshot it does work with the Magic TrackPad in CT?
Anyway, I created a shortcut to make it possible to consult the dictionary, but it shows the Dictionary.app window, not the nice pop-up thingie (see screenshot above).
Ipse dixit: but it shows the Dictionary.app window, not the nice pop-up thingie
Blast! It does (the shortcut, that is):
May not be available for Magic Mouse...
I use Apple's Trackpad for this.
If you have a MacBook series, you can find it out.
One more (just to show off):
OK, so it seems to be a MM "problem."