dictionary
OSX always tries to autocorrect the the unix commands that I save into my note taking application.
To prevent this, I right click and tell OSX to "Learn Spelling".
Is there a way to teach this spelling to all my Mac's? Ideally using iCloud or dropbox.
Removing words from the built-in dictionary is apparently more difficult than I thought it would be. Since your question is about how to prevent a particular misspelling of your co-worker's name, I have an alternate solution.
You can add "Jennet" to Mac OS X's text substitution list in System Preferences -> Language & Text -> Text
It will automatically correct the spelling for you each time you misspell it. You could add other variant misspellings for completeness, like "Jenet" or even make it auto-capitalize "jennett", but since most other misspelling variants don't have obscure English homonyms these will show up as misspellings.
There is a freeware, Language Switcher, to launch an app in a different language.
Or, you check another thread for more detail: Is it possible to launch a program in a specific language?
Best Answer
The spellings are located in various files in
~/Library/Spelling. Namely, LocalDictionary and various localisation files such as en_GB. You can sync this entire folder using a sync method of your choice.~/Library/Mobile Documents.