This Counter32 counts packets that were sent successfully but whose first transmission attempt was delayed because the port found the medium already busy. It reflects carrier-sense deferral rather than a collision, so a climbing count means the segment is often busy right when this port wants to talk, not necessarily a fault. An admin seeing high txDeferredTransmit on one port of the CMM-III might conclude that port's link is shared with heavier traffic than the others and consider moving a device to a quieter port.