Someone who is a member of a specialized patent prosecution bar but is not necessarily (and frequently is not in fact) a lawyer. Patent agents (Patent Attorneys in the U.K., Benrishi in Japan) are members of a separate profession to lawyers, have specialized training in the drafting and prosecution of patents, usually must have an engineering or science degree, and have passed a special exam.
In many jurisdictions, e.g., the United States, only a patent agent may file a patent application on an inventor’s behalf, although inventors may (usually unwisely) choose to represent themselves. In Europe, few patent agents are also lawyers (i.e., solicitors or barristers); in the U.S. many, if not the majority of patent agents are also lawyers (i.e., attorneys-at-law).
The term patent lawyer is sometimes used in Europe to denote a lawyer who specializes in patent law—but the term does not necessarily denote that the person is a patent agent, and in Europe a patent lawyer is probably not also a patent agent. Whether the agent is, or is not a lawyer, is not simply a matter of legal snobbery; client communications with lawyers as well as the lawyer’s internal work product enjoy broad legal Privilege. By contrast, communications with a patent agent may not have the same degree of protection.