11-Letter Words Matching ____C____U_

There are 20 11-letter words that match ____C____U_. 5 are common words, such as EFFICACIOUS and IMPECUNIOUS. A rarer one is BREECHCLOUT. In this set, O is the most frequent open letter (16 words). 3 words contain a doubled letter.

Full list 20

efficaciousimpecuniousovercarefulpericardiumtreacherousacrocarpousaltocumulusendocardiumendocraniumindeciduousinsectariummonochasiummonoclinousovercuriouspenicilliumpericraniumpolychasiumsalicaceousurticaceousbreechclout

About this list

Words
20 (5 common words)
Common example
efficacious
Rare example
breechclout
Doubled letters
3
Ending in S
10
Most frequent letter
O (16)

Questions

How many 11-letter words matching ____c____u_ are there?

20. 5 of them are common words.

What is a common example?

EFFICACIOUS is among the common words in this set.