libeler vs defamer

libeler and defamer both are nouns.

Word	Noun	Adjective	Verb	Adverb
libeler	Yes	No	No	No
defamer	Yes	No	No	No

As nouns, libeler and defamer are synonyms defined as:

libeler and defamer: one who attacks the reputation of another by slander or libel

Other synonyms of libeler include backbiter, maligner, slanderer, traducer, vilifier.

libeler (noun)	defamer (noun)
one who attacks the reputation of another by slander or libel	one who attacks the reputation of another by slander or libel