then what is a money transmitter
It depends on who's definition. Generally speaking well written statutes will define key terms but there are a lot of horribly written laws on the books. At the federal level it is defines as:
(5) Money transmitter —(i) In general. (A) A person that provides money transmission services. The term “money transmission services” means the acceptance of currency, funds, or other value that substitutes for currency from one person and the transmission of currency, funds, or other value that substitutes for currency to another location or person by any means. “Any means” includes, but is not limited to, through a financial agency or institution; a Federal Reserve Bank or other facility of one or more Federal Reserve Banks, the Board of Governors of the Federal Reserve System, or both; an electronic funds transfer network; or an informal value transfer system;
http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&SID=1874ed9b8ba25f5cf9527e5e39a28df8&rgn=div5&view=text&node=31:3.1.6.1.2&idno=31#31:3.1.6.1.2.1.3.1FinCEN guidance in April states that it is their interpretation that the conversion of virtual currency into real currency or real currency into virtual currency meets this definition.
In WA (for the purpose of state laws/regs/licensing) however it is defined simply as this:
(19) "Money transmitter" means a person that is engaged in money transmission.
Hmm. Well that doesn't tell us a whole lot. Lets see if money transmission is defined.
(18) "Money transmission" means receiving money or its equivalent value to transmit, deliver, or instruct to be delivered the money or its equivalent value to another location, inside or outside the United States, by any means including but not limited to by wire, facsimile, or electronic transfer. "Money transmission" does not include the provision solely of connection services to the internet, telecommunications services, or network access. "Money transmission" includes selling, issuing, or acting as an intermediary for open loop stored value devices and payment instruments, but not closed loop stored value devices.
Does exchanging BTC for USD meets this definition. Well it depends on what "money" is doesn't it. Luckily that is defined as well.
(16) "Money" means a medium of exchange that is authorized or adopted by the United States or a foreign government or other recognized medium of exchange. "Money" includes a monetary unit of account established by an intergovernmental organization or by agreement between two or more governments.
So is Bitcoin "money" under WA law? Well a case could be made that it isn't as no government, international body, intergovernmental organization has stated Bitcoin is "money". Virtual currency yes but money no. Still WA is one of those states that likely it won't be decided until either it ends up in court or the law is ammended to be more explicit.
Lets look at another example state, Utah:
This rule applies to any individual or other party who issues, sells or offers to sell within the state any instrument for the purpose of effecting payments to third parties, including, but not limited to, money orders, traveler's checks, and the wire transmission of money.
Key word is "for the purpose of payments to third parties. If there is no third party then is there a money transmitter? This isn't legal advice but a credible case could be made that a company (the first party) buying Bitcoins from you (the second party) and paying the proceeds in USD to the same party (you) would not meet the definition of money transmitter under UT law.
Some states are just mute on the entire topic. In Alaska's general code for example the words "money transmitter" simply don't exist. Under Alaskan law there is no such thing as a money transmitter any more then there is a flux capacitor repairman.
TL/DR: So the answer really depends on "according to who" and in what context. The important thing is that no two states define "money transmitter", "money transmission", or even "money" the same. Some definitions are very specific and exclude Bitcoin by omission, some definitions like WA are vague and really can only be definitively decided in court. Some definitions are so asininely broad that "money transmission" could include just about anything including the buying, selling, or exchanging of bennie babies ... if a prosecutor so wanted.
DISCLAIMER: I AM NOT A LAWYER. IF YOU NEED LEGAL ADVICE ON YOUR PARTICULAR SITUATION THE ONLY ACCEPTABLE SOLUTION IS TO RETAIN INDEPENDENT LEGAL COUNSEL. PERIOD. The above post is just intended to be educational and highlight that context matters.
