To liaise is to keep talking with someone in another team, office, or group so both sides know what the other is doing and the work fits together. You can liaise by email, phone, or meetings; it is not the same as meeting once, and it is not quite the same as helping. British offices like this word. Americans often skip it and say “work with” or “coordinate with” instead. It sounds a little official — companies, schools, and government use it more than friends at dinner. You liaise with a person or a department, or you liaise between two groups. Though actually, people stretch it: “I’ll liaise with them” can just mean “I’ll be the one who talks to them,” even if nothing very organised is happening.