"What does 'disable' actually mean?" – drones are generally...

"What does 'disable' actually mean?" – drones are generally programmed to either land or return home when they lose communications. The return home option is generally programmed into the more expensive units that track their position using a combination of GPS and inertial data so they have some idea of where "home" is. Most will just descend vertically until they touch ground.

All kinds of payload scenarios are possible, including detonation on contact (i.e. landing). Security services using counter-drone devices would have to consider these scenarios in their risk mitigation planning. It's not strictly a defeat issue. In the presidential inauguration scenario, I would have tried to control the crowd to provide a clear zone between the crowd and the president where a potentially explosive drone could be dropped.

Similarly, there are all kinds of ways to program a drone to behave when communication is lost: drop its payload, hover or fly randomly until the battery goes flat, drop dead. The key thing is that it's no longer being controlled by a malicious agent.

You can pick up most of this information from the Droneshield website and the investor presentation.