Ponzi scheme. Definition.
A type of investment fraud in which investors are promised artificially
high rates of return with little or no risk; original investors and the
perpetrators of the fraud are paid off by funds from later investors,
but there is little or no actual business activity that produces revenue.
Ref: https://www.law.cornell.edu/wex/ponzi_scheme

Pyramid Schemes vs Multi-Level Marketing (MLM)
Pyramid Schemes Have Only One Purpose. The big difference between
multilevel marketing and a pyramid scheme is in the way the business operates.
The entire purpose of a pyramid scheme is to get your money and then
use you to recruit other suckers (ahem - distributors).
The main purpose of MLM is to sell product through it's distributors.
Ref: Google

Investment
To invest is to allocate money (or sometimes another resource, such as time)
in the expectation of some benefit in the future, for example,
investment on durable good such as real estate for service industry
and factory for manufacturing product development, which are two
common types for micro-economic output in modern economy.
Investment on Research and Development occurs mainly on the innovation of consumer products.
Ref: wikipedia

Currency Trading
Currency Trading is the act of buying and selling (trading) different currencies
of the world. The Foreign Exchange (or Forex) is the market that
allows you to trade currencies in volume.

bitconnect
- High Rate of Return - Yes
- Little or no risk - No
- Funded by investors/distributors - Yes
- Product to Sell - Maybe

Questions?
Is BCC really a crypto-currency like Bitcoin?
Is the funding an investment in BCC or just moving money and getting paid to do so with fees?
Do they really trade in Bitcoin or other crypto-currencies independently of the members?
How much money is in their BTC/BCC bank and is there any accountability?

These are critical questions to the legitimacy of the company.

Ponzi/Pyrimad Scheme vs MLM vs Currency Exchange?
At what point does one definition cross over to another?

Looking forward to see how this plays out as it will affect other businesses that
operate in a similar way and the Crypto-currency community as a whole.

Also, the definitions are examples only and each one has had thousands of books written about the subject.