13-Letter Words Matching O_______O____

There are 24 13-letter words that match O_______O____. 8 are common words, such as OBSERVATORIES and ONOMATOPOEIAS. A rarer one is OVERZEALOUSLY. In this set, I is the most frequent open letter (18 words). 5 words contain a doubled letter.

Full list 24

observatoriesonomatopoeiasonomatopoeticophthalmologyopprobriouslyornithologiesornithologistovershadowingodoriferouslyovariectomiesoverelaborateodontoglossumonomatologiesonomatologistonychophoransoppositionistoverborrowingoverdiscountsoverexploitedoverglamorizeoverpromotingoverrespondedoverseriouslyoverzealously

About this list

Words
24 (8 common words)
Common example
observatories
Rare example
overzealously
Doubled letters
5
Ending in S
7
Most frequent letter
I (18)

Questions

How many 13-letter words matching o_______o____ are there?

24. 8 of them are common words.

What is a common example?

OBSERVATORIES is among the common words in this set.