1. A hall, foyer, or waiting room at or near the entrance to a building; such as, a hotel or theater.
2. A public room next to the assembly chamber of a legislative body.
3. A group of persons engaged in trying to influence legislators or other public officials in favor of a specific cause; such as, the banking lobby; the labor lobby.
4. To try to influence public officials on behalf of or against (proposed legislation, for example); such as, lobbied the bill through Congress; lobbied the bill to a negative vote.
5. To try to influence (an official) to take a desired action.

From 1593, an entrance hall, passageway, in Shakespeare's 2 Henry VI; earlier, cloister or covered walk (1533); borrowed from Medieval Latin lobia, "covered walk"; from a Germanic source (laubja, "shelter").

The referece to people who try to influence legislators is first recorded in 1808 in American English, from the lobbyists' custom of gathering in the lobby outside a legislative chamber. Such a lobby, originally (1640) referred to the one in the British House of Commons, and was called the Lobby, serving chiefly for interviews between members and people who did not belong to the House.

1. To make an effort to influence the thinking of legislators or other public officials for or against a specific cause: such as, lobbying for stronger environmental safeguards; lobbied against the proliferation of nuclear weapons.
2. To try to influence (an official) to take a desired action.