NameThatUI is a visual reference dictionary for user interface elements, covering both macOS AppKit/SwiftUI components and web UI patterns. Users describe or browse UI elements to learn their correct technical names, framework symbols, and HTML or API identifiers. The tool is designed to help developers and designers write precise prompts for coding agents by giving them the exact terminology used in AppKit, SwiftUI, and web standards. It catalogs over 60 named elements across macOS and web contexts, including a searchable translation table mapping plain names to AppKit and SwiftUI equivalents. A companion visual styles atlas helps users identify and name design aesthetics as well.