I notice Megachurch has been defined down to include any church with over 2000 people, and defined further to exclude the definer's own denomination, because in total they could be hundreds of times larger. Then, the leftovers are put in the same basket. Basically, analysis worthy of a kindergartener.
Actually, the 2000 figure (attendance per week, as many churches do not have actual members) has been true for years as the average membership in churches in the US is 180, IIRC.
Someone recently coined the word "GigaChurch" to describe churches that have weekly attendance of 10,000 or more.
My church falls into the latter category.