A 3D pumpkin is a digital model of a traditional pumpkin, rendered in three dimensions. It is typically created using a computer coding language such as HTML (Hypertext Markup Language) and displayed on a screen as a 7.5x7.5 inch image. This size may vary, as it is dependent on the dimensions set by the coder. The "en_US" in the description refers to the language and location settings, with "en" standing for English and "US" indicating the United States. This is often used to specify the audience for the content, as language and cultural references may differ in different regions.