Primness is the characteristic of being fussily formal. Your primness might keep you sitting politely on the sofa during the party, instead of running around blowing noisemakers with the other guests.
Someone who's prim is extremely respectable and particular, often frowning in disapproval at other people. This quality is primness. The primness of your new teacher's face on the first day of school may give you a clue about how much fun the year will be — despite the appearance of primness, however, your teacher may surprise you by throwing frequent pizza parties. The Latin root, primus, means "finest."