Final answer:
The root 'mega-' in 'megaphone' means 'huge.' It signifies something great or large in scale, as seen in other words such as 'megapixel' and 'megaton'.
Step-by-step explanation:
The root mega- in the word megaphone means huge or large in scale. This root word comes from the Greek “megas,” which translates to “great” or “large.” Therefore, a megaphone is a device intended to amplify a voice to cover a large area or to reach a huge crowd. Other examples of words with the mega- root include megapixel, which represents a huge number of pixels, and megaton, which is a unit of explosive power equivalent to one million tons.