If somebody has a guest, it is already assumed that the guest was invited to partake of the hospitality and entertainment of his his; hence avoid using the phrase "an invited guest" as it is redundant, and what's more -- tautological. Guests by definition are invited.
By definition, all guests are invited, therefore an "uninvited guest" is also pointless, and an oxymoron, to boot.
Refrain from use of either of these phrases and I'll give you a gold star on your grammar star chart.
Need help practicing your oxymorons. I invite you to play the oxymoron game. Be my guest!
What's interesting is that so many common expressions are oxymorons:
- loosely packed
- instant classic
- act natural
- irregular pattern
- slumber party