clowning vs japery

clowning and japery both are nouns.

Word	Noun	Adjective	Verb	Adverb
clowning	Yes	No	No	No
japery	Yes	No	No	No

As nouns, clowning and japery are synonyms defined as:

Other synonyms of clowning include buffoonery, frivolity, harlequinade, prank.

clowning (noun)	japery (noun)
acting like a clown or buffoon	acting like a clown or buffoon
a comic incident or series of incidents