To smile or laugh mockingly or disrespectfully; to sneer or gibe at someone.
From Old Norse 'flira' (to grin scornfully), reflecting the Scandinavian influence on English vocabulary. The word originally meant to show one's teeth in disdain, evolving from a physical gesture to the act of mocking.
Viking languages gave English 'fleer,' and it's barely used today except in Shakespeare—but it's more specific than 'mock' because fleer involves that contemptuous grin, the physical expression of superiority.
Complete word intelligence in one call. Free tier — 50 lookups/day.