I know of no definitions under which investments must be risky. Investments are "a commitment (of time, money, etc) in order to earn a return" (not a direct quote, but a fusion of Merriam-Webster's definitions of invest and investment). Nowhere in there (or any of the other definitions of invest/investment) is risk mentioned.
All investments are guaranteed returns? News to me... All my money into Target stock! All investment implies risk and I wouldn't learn financials (or anything) merely from Merriam-Webster definitions.
