9-Letter Words Matching _____O_P_

There are 13 9-letter words that match _____O_P_. 2 are common words, such as MESOMORPH and SUBGROUPS. A rarer one is SANDSOAPS. In this set, R is the most frequent open letter (11 words). 2 words contain a doubled letter.

Full list 13

mesomorphsubgroupsallomorphectomorphendomorphlagomorphparamorphperimorphhypomorphoutgroupsoutscoopspolymorphsandsoaps

About this list

Words
13 (2 common words)
Common example
mesomorph
Rare example
sandsoaps
Doubled letters
2
Ending in S
4
Most frequent letter
R (11)

Questions

How many 9-letter words matching _____o_p_ are there?

13. 2 of them are common words.

What is a common example?

MESOMORPH is among the common words in this set.