Defamation is the publication of a statement which refers on a
person’s reputation and tends to lower him in the estimation of
right-thinking members of society generally or tends to make then
shun or avoid him.
“Published” doesn’t have to mean printed in a newspaper. It can
be said on a TV program, on the radio, in a speech, printed on
flyers – basically, it has to be spread somehow,
intentionally.
Libel typically refers to publishing something that’s
permanent. A newspaper.
If the statement is made in writing and published, the
defamation is called "libel." If the hurtful statement is spoken,
the statement is "slander."