According to Dictionary.com, here is the definition of cupcake -
"a small cake, the size of an individual portion, baked in a cup-shaped mold."
According to my husband, -
"anything with frosting on it."
This was very relevant indeed this morning at 6am as I was baking Cinnamon Sugar-Puff Cupcakes, from the amazing book cupcakes! by Elinor Klivans