Unshirted is an adjective that means undisguised or plain.

Coming from two common English words, unshirted can simply mean ‘not wearing a shirt,’ but it also means ‘without a disguise.’ Here’s an example of it in use:

It seems to me that the mayor would have been better off making unshirted demands instead of disguising his needs with fancy words. The more plain his speech, the easier it is to accommodate him.