A drench is an intense amount of water or liquid that falls suddenly.
Imagine you're walking outside on a sunny day and then out of nowhere a heavy downpour hits. That's what it means to get drenched – completely soaked by rain or another kind of liquid. This can happen quickly, like when driving through a flooded street and getting your car wet, or more slowly over time, such as during a long hike in the rain where you keep getting splashed with water. In both cases, the result is that you get really, really wet – completely drenched!
A draught administered to an animal.
To soak, to make very wet.
