Often used by someone with authority against inappropriate behavior or ideas. The judge slapped down the lawyer's objection during the trial.
Pro Tip 2/3
Public Embarrassment
May imply a public correction, causing embarrassment for the person being corrected. At the meeting, the director slapped down the intern in front of everyone.
Pro Tip 3/3
Assert Dominance
Can be used to display dominance and control over a situation or person. The CEO slapped down dissenting voices during the merger discussion.