15-Letter Words Matching O_____O________

There are 13 15-letter words that match O_____O________. 4 are common words, such as OBLIVIOUSNESSES and OBNOXIOUSNESSES. A rarer one is OVERPROPORTIONS. In this set, I is the most frequent open letter (13 words). 6 words contain a doubled letter.

Full list 13

obliviousnessesobnoxiousnessesofficiousnessesoverproductionsopisthognathousornithorhynchusorthodonticallyoverprotectionsorthogonalitiesorthogonalizingoscillographiesoverprogrammingoverproportions

About this list

Words
13 (4 common words)
Common example
obliviousnesses
Rare example
overproportions
Doubled letters
6
Ending in S
10
Most frequent letter
I (13)

Questions

How many 15-letter words matching o_____o________ are there?

13. 4 of them are common words.

What is a common example?

OBLIVIOUSNESSES is among the common words in this set.