13-Letter Words Matching _O__________R

There are 20 13-letter words that match _O__________R. 3 are common words, such as CONCERTMASTER and COUNTERFEITER. A rarer one is NONPROGRAMMER. 7 words contain a doubled letter.

Full list 20

concertmastercounterfeiterfortunetellercongratulatorconventioneermonomolecularpotentiometerrollercoasterzoogeographercoconspiratorconglomeratorcounterplayercountersnipercounterterrordoublespeakermonochromatornonchurchgoernoncompetitornoncooperatornonprogrammer

About this list

Words
20 (3 common words)
Common example
concertmaster
Rare example
nonprogrammer
Doubled letters
7
Ending in S
0

Questions

How many 13-letter words matching _o__________r are there?

20. 3 of them are common words.

What is a common example?

CONCERTMASTER is among the common words in this set.