a room providing a space out of which one or more other rooms or corridors lead, typically one near the entrance of a public building

they went into the hotel lobby

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

a group of people seeking to influence legislators on a particular issue

contact an anti-traffic lobby for advice and information

seek to influence (a legislator) on an issue

they insist on their right to lobby Congress

the organization was formed to lobby for student concerns