lobbyist

Concise Oxford English Dictionary © 2008 Oxford University Press:
lobby/ˈlɒbi/

▶noun (pl. lobbies)

• 1 a room out of which one or more other rooms or corridors lead, typically one near the entrance of a public building.

• 2 (in the UK) any of several large halls in the Houses of Parliament in which MPs may meet members of the public.

  ■ (also division lobby) each of two corridors in the Houses of Parliament to which MPs retire to vote.

• 3 a group of people seeking to influence legislators on a particular issue.

  ■ an organized attempt by members of the public to influence legislators.

▶verb (lobbies, lobbying, lobbied) seek to influence (a legislator).

– derivatives
lobbyist noun.

– origin C16 (in the sense ‘monastic cloister’): from med. L. lobia, lobium ‘covered walk’.