To meet is to intentionally enter a live communications activity with one or more other agents.
A meeting is a time-limited (periodic) event during which two or more agents mutually agree to be present, giving attention to each other's actions, especially signals.
Note that as defined above, meetings do not include all in-person interactions. The essence of meeting is mutual understanding of planned co-presence and attention.
Meetings are often officially planned and scheduled, but they may emerge spontaneously.