Obstacle and Snarl-up

Obstacle noun - Something that makes movement or progress difficult.

Snarl-up and obstacle are semantically related. In some cases you can use "Snarl-up" instead a noun "Obstacle".

Snarl-up noun - A number of vehicles blocking one another until they can scarcely move.

Obstacle and snarl-up are semantically related. Sometimes you can use "Obstacle" instead a noun phrase "Snarl-up".