Well let's look at what the dictionaries say(top 3 google results for "currency dictionary"):
(I will underline what I think describes Bitcoins)
cur·ren·cy [kur-uhn-see, kuhr-] Show IPA
–noun, plural -cies.
1.
something that is used as a medium of exchange; money.
2. general acceptance; prevalence; vogue.
3. a time or period during which something is widely accepted and circulated.
com·mod·i·ty [kuh-mod-i-tee] Show IPA
–noun, plural -ties.
1.
an article of trade or commerce, especially a product as distinguished from a service.2.
something of use, advantage, or
value.
3. Stock Exchange .
any unprocessed or partially processed good, as grain, fruits, and vegetables, or precious metals.
mon·ey [muhn-ee] Show IPA
noun, plural mon·eys, mon·ies, adjective
–noun
1.
any circulating medium of exchange, including coins, paper money, and demand deposits.
2. paper money.
3. gold, silver, or other metal in pieces of convenient form stamped by public authority and issued as a medium of exchange and measure of value.
http://dictionary.reference.com/cur·ren·cy (kûrn-s, kr-)
n. pl. cur·ren·cies
1. Money in any form when in actual use as a medium of exchange, especially circulating paper money.
2.
Transmission from person to person as a medium of exchange; circulation: coins now in currency.3. General acceptance or use; prevalence: the currency of a slang term.
4. The state of being current; up-to-dateness: Can you check the currency of this address?
currency [ˈkʌrənsɪ]
n pl -cies
1. (Economics, Accounting & Finance / Currencies)
a metal or paper medium of exchange that is in current use in a particular country2. general acceptance or circulation; prevalence the currency of ideas
3. the period of time during which something is valid, accepted, or in force
4. the act of being passed from person to person
5. (Economics, Accounting & Finance / Currencies) Austral (formerly)
the local medium of exchange, esp in the colonies, as distinct from sterling
6. (Social Science / Peoples) Austral slang (formerly) the native-born Australians, as distinct from the British immigrants
[from Medieval Latin currentia, literally: a flowing, from Latin currere to run, flow]
com·mod·i·ty (k-md-t)
n. pl. com·mod·i·ties
1.
Something useful that can be turned to commercial or other advantage: "Left-handed, power-hitting third basemen are a rare commodity in the big leagues" (Steve Guiremand).
2.
An article of trade or commerce, especially an agricultural or mining product that can be processed and resold.3. Advantage; benefit.
4. Obsolete A quantity of goods.
commodity [kəˈmɒdɪtɪ]
n pl -ties
1. (Economics)
an article of commerce2. something of use, advantage, or profit
3. (Economics) Economics
an exchangeable unit of economic wealth, esp a primary product or raw material4. Obsolete
a. (Economics) a quantity of goods
b. convenience or expediency
[from Old French commodité, from Latin commoditās suitability, benefit; see commodious]
mon·ey (mn)
n. pl. mon·eys or mon·ies
1.
A medium that can be exchanged for goods and services and is used as a measure of their values on the market, including among its forms a commodity such as gold, an officially issued coin or note, or a deposit in a checking account or other readily liquefiable account.
2. The official currency, coins, and negotiable paper notes issued by a government.
3.
Assets and property considered in terms of monetary value; wealth.
4.
a. Pecuniary profit or loss: He made money on the sale of his properties.
b. One's salary; pay: It was a terrible job, but the money was good.
5. An amount of cash or credit: raised the money for the new playground.
6. Sums of money, especially of a specified nature. Often used in the plural: state tax moneys; monies set aside for research and development.
7. A wealthy person, family, or group: to come from old money; to marry into money.
http://www.thefreedictionary.com/cur·ren·cy noun \ˈkər-ən(t)-sē, ˈkə-rən(t)-\
plural cur·ren·cies
Definition of CURRENCY
1
a :
circulation as a medium of exchangeb : general use, acceptance, or prevalence <a story gaining currency>
c : the quality or state of being current : currentness
2
a :
something (as coins, treasury notes, and banknotes)
that is in circulation as a medium of exchangeb : paper money in circulation
c :
a common article for barteringd : a medium of verbal or intellectual expression
See currency defined for English-language learners »
See currency defined for kids »
Examples of CURRENCY
A new currency has been introduced in the foreign exchange market.They were paid in U.S. currency.Furs were once traded as currency.The word has not yet won widespread currency.
I'm not sure about the accuracy and currency of their information.
com·mod·i·ty noun \kə-ˈmä-də-tē\
plural com·mod·i·ties
Definition of COMMODITY
1
: an economic good: as
a : a product of agriculture or mining
b :
an article of commerce especially when delivered for shipment <commodities futures>
c :
a mass-produced unspecialized product <commodity chemicals> <commodity memory chips>
2
a :
something useful or valued <that valuable commodity patience>; also :
thing, entityb : convenience, advantage
3
obsolete : quantity, lot
4
: a good or service whose wide availability typically leads to smaller profit margins and diminishes the importance of factors (as brand name) other than price
5
: one that is subject to ready exchange or exploitation within a market <stars as individuals and as commodities of the film industry — Film Quarterly>
See commodity defined for English-language learners »
See commodity defined for kids »
Examples of COMMODITY
agricultural commodities like grain and corn
Oil is a commodity in high demand.
Patience is a rare commodity.
1
mon·ey noun, often attributive \ˈmə-nē\
plural moneys or mon·ies
Definition of MONEY
1
: something generally accepted as a medium of exchange, a measure of value, or a means of payment: as
a : officially coined or stamped metal currency
b :
money of accountc : paper money
2
a : wealth reckoned in terms of money
b : an amount of money
c plural : sums of money : funds
3
:
a form or denomination of coin or paper
money4
a : the first, second, and third place winners (as in a horse or dog race) —usually used in the phrases in the money or out of the money
b : prize money <his horse took third money>
5
a : persons or interests possessing or controlling great wealth
b : a position of wealth <born into money>
http://www.merriam-webster.com/dictionary/