Lobbyist (noun)

1. A person who tries to influence government decisions on behalf of a particular group or interest.
2. A person who works to influence decisions made by an organization or an association.

Origin:

Mid 19th century: from lobby, on the pattern of agent.

Examples:

1. The lobbyist met with the senator to discuss the proposed bill.
2. The company hired a lobbyist to represent their interests in the government.
3. The lobbyist tried to influence the legislation in favor of his clients.
4. The environmental group had a lobbyist at the United Nations conference.
5. The trade association had a team of lobbyist working on the issue.