hi·lar·i·ty \hə̇ˈlarəd.ē, -ətē, -i also hīˈ- or -ler-\noun (-es) Etymology: Middle French hilarité, from Latin hilaritat-, hilaritas, from hilarus, hilaris + -itat-, -itas -ity 1.: temperate gaiety : cheer, cheerfulness < wine gives not light, gay, ideal hilarity but tumultuous, noisy, clamorous merriment — Samuel Johnson > 2.: boisterous merriment : intense mirth or laughter < in a continual gale of hilarity >