Hi,
When the same interface is sharing L2 network with more than 1 router, it is multi-access. Quick example is Ethernet.
|------B
A-----|
|-------C
Assume GigabitEthernet0/0 of Router , B and C are connected to same L2 network, the interface on A (or B, C) is multi-access A can use this interface to reach B and C. This is Broadcast multi-access. Other example is FR/ATM which is Non Broadcast multi-access (NBMA).
-Nagendra