a large entrance or reception room or area
"The grand lobby of the hotel featured a towering crystal chandelier and marble floors."
the people who support some common cause or business or principle or sectional interest
"The powerful lobby successfully pressured lawmakers to pass the new environmental regulations."
an interest group that tries to influence legislators or bureaucrats to act in their favor, typically through lobbying
"The oil lobby successfully convinced congressmen to vote against stricter emissions regulations."
An entryway or reception area; vestibule; passageway; corridor.
"The sailor ordered a bowl of hot scouse to warm up after his long shift at sea."
scouse (from lobscouse)
In plain English: A lobby is an open room at the entrance of a building where people wait, gather, or pass through to get inside other areas.
"We waited in the hotel lobby to meet our friends at check-in time."
Usage: As a noun, "lobby" refers specifically to an entrance hall or waiting room where people gather before entering the main building. Do not confuse this physical space with the verb form meaning to attempt to influence public officials through persuasion.
detain in conversation by or as if by holding on to the outer garments of; as for political or economic favors
"The lobbyist managed to lobby the senator into delaying the vote by clasping his arm and pleading for a temporary postponement."
To attempt to influence (a public official or decision-maker) in favor of a specific opinion or cause.
"The environmental group gathered outside the mayor's office to lobby for stricter air quality regulations."
In plain English: To lobby means to try hard to persuade someone, usually a politician, to vote your way on something important.
"She tried to lobby her friend for support on the project."
The word "lobby" comes from Medieval Latin through Frankish, originally meaning a covered walkway or arbour with foliage. Its political sense developed in English to describe the entrance halls of legislatures where people gathered to influence lawmakers.