He snorted at the rumors and never paid them any mind.
Tips
history
Echoes the anecdote in 《后汉书·樊宏传》 where Fan Hong planted trees long before needing the wood, and his contemporaries 嗤之 ('snorted at him'). The fixed four-character form 嗤之以鼻 developed later.
usage
Structure: 对 [X] 嗤之以鼻. Strong literary flavor — implies looking down on something as unworthy of serious response. Common targets: rumors, pseudo-science, bad arguments. Contrast with 不屑一顾 (not deigning to glance).