As the ancients said: to defame in one's belly and slander in one's heart (i.e. silent disapproval).
Tips
usage
诽 rarely stands alone in modern Chinese — almost always part of compounds: 诽谤 (fěibàng, to defame/slander, in legal language), 腹诽 (fùfěi, silent inner criticism), 怨诽 (yuànfěi, to gripe and slander).
memory
Note 《说文》: 谤 is open accusation; 诽 is muttered behind the back. The 言 'speech' radical + 非 'wrong' hints at 'words against' — speech directed at someone's faults.
