According to the Apple Dictionary...
incognito |ËŒinkägˈnÄ“tÅ; inˈkägniËŒtÅ|
adjective & adverb
(of a person) having one's true identity concealed : [as adj. ] in order to observe you have to be incognito | [as adv. ] he is now operating incognito.
noun ( pl. -tos)
an assumed or false identity
Just to clarify... That's the definition that's returned by command-control-D and "Dictionary" in Dictionary.app; (the) "Apple" (Dictionary) therein returns "No entries found." (The Apple Dictionary includes
[more or less?] Apple/computing related terms only, which can be demonstrated by launching Dictionary.app, selecting "Apple," and entering single letters in the search field.)