A curlicue is a spiral, twist, or wavy shape that's added as a flourish. You might personalize your signature by adding a couple of curlicues to the first letter of your name.
In design, architecture, and works of art, a curly spiral can be called a curlicue. The black wrought iron fence surrounding a rose garden may feature curlicues, and formal calligraphy, with its swirls and flourishes, is full of curlicues. This word is an Americanism based on curly, with the cue probably stemming from the French queue, "tail." An earlier — and more adorable — word with the same meaning was curlie-wurlie.