Don't go around mocking and slandering others behind their backs.
Tips
usage
Two flavors: 讪笑 (to laugh at / sneer) and 讪谤 (to slander). But 讪讪 means 'embarrassed, sheepish' - the face you make when caught out, as in 讪讪地走开 (slink off in embarrassment).
Speech radical on the left, side-form of 言. It marks an act of words - here mocking or slanderous speech. Same family as 讽 to satirize, 谤 to defame, 讥 to taunt.
Right side 山 supplies the sound (shān to shàn, a tone shift). It is purely phonetic; the mountain shape carries no meaning into this 'to ridicule' word.
