Popular Courses. Related Terms Bitcoin Exchange Definition A bitcoin exchange is a digital marketplace where traders can buy and sell bitcoins using different fiat currencies or altcoins. Some users protect their private keys by encrypting a wallet with a strong password and, in some cases, by choosing the cold storage option; that is, storing the wallet offline. Best for Versatility: Square Cash. The surge and volatility of bitcoin this year may be great for those who invested early, but it undermines bitcoin’s viability as a currency. For 15 minutes at the airport, I refreshed the price of bitcoin over and over, watching as it gained and lost hundreds of dollars in a matter of minutes. My wife’s opinion of me has reportedly decreased by the same amount.