It's the systemwide spelling checker. (The thing that makes the little dotted red lines appear under misspelled words in Safari, Mail, Pages, Keynote....)
It shouldn't be visible. Services are supposed to do their work without being seen. Sort of like well-disciplined servants.
Anyway, try this.
- In the Finder, navigate to the Services folder.
Your Hard Disk: System: Library: Services:
The AppleSpell.service bundle should be there.
- Control-click on it and choose "Show Package Contents" from the context menu
You should get a window with a Contents folder inside.
- Open the Contents folder.
You should see a bunch of files, one of which should be Info.plist
- Open Info.plist. If you have the developer tools installed, Info.plist should open with in the Property List Editor. If not, you can open it with a text editor
I'm willing to bet that somewhere the LSBackgroundOnly key is followed by a string that is something other than 1.
- Change that string to 1, and you shouldn't see the spelling service again.
(If there is no LSBackgroundOnly key, you can add one and give it a string equal to 1. If you need help doing this, just ask.)