abuse, slander, vilify, ridicule
訕 centers on attacking someone's reputation through speech: abusing, slandering, vilifying, or ridiculing them.
訕 combines 言 (speech) with 山, which likely contributes the sound. The character expresses verbal abuse or slander.
Words 言 piled up like a mountain 山 of insults: abuse, slander, and ridicule.
For サン, imagine a slanderous person shouting insults from a mountain 山 top, their voice echoing 'san, san, san'.