13-Letter Words Matching O_________O__

There are 19 13-letter words that match O_________O__. 8 are common words, such as OBLITERATIONS and OPHTHALMOLOGY. A rarer one is OVERTAXATIONS. In this set, S is the most frequent open letter (18 words). 3 words contain a doubled letter.

Full list 19

obliterationsophthalmologyoptimizationsorganizationsossificationsoverambitiousoverexertionsoverreactionsorchestratorsorthognathousoverrighteousovoviviparousobnubilationsoptimisationsorganisationsoverconsciousovercredulousoveringeniousovertaxations

About this list

Words
19 (8 common words)
Common example
obliterations
Rare example
overtaxations
Doubled letters
3
Ending in S
18
Most frequent letter
S (18)

Questions

How many 13-letter words matching o_________o__ are there?

19. 8 of them are common words.

What is a common example?

OBLITERATIONS is among the common words in this set.