Wiktionary
snarl up
vb. 1 (context transitive English) to entangle 2 (context intransitive English) To become tangled; to become entangled 3 (context transitive English) To block (traffic); to cause (traffic) to be congested. 4 (context intransitive of traffic English) to become congested. 5 (context transitive English) To pit into disarray; contort; confuse; muddle up
WordNet
Usage examples of "snarl up".
I felt my upper lip twitch, as if to snarl up and bare my pitiful human teeth.
Aircars were so nearly accident-proof that even Plemponi couldn't do more than snarl up traffic in one.
The ladder pivoted lightly from side to side under his weight, but so long as it didn't snarl up altogether, that was all right.
It'll snarl up the whole ring and give us time to get under cover by those transports.