A strange verb often found when describing traffic jams or bottlenecks.
There is a snarl up on the expressway north of the city. Traffic is banked up for 3 kilometres.
The idea behind it is that of something being twisted up and not flowing freely.
The fishing lines tend to get snarled up on the rocks if you don’t cast out far enough.
Snarl by itself is perhaps more commonly used for the growling sound an angry dog uses.
As the stranger approached, my dog started snarling warning me that something was not right about this person.