adverb taking the 'to' particle
with a wriggle; slitheringly; squirtingly
Describes a smooth, slippery, or wriggling motion, often of something long and thin like a snake, worm, or noodle, or a sudden spurt of liquid.
ヘビがにゅるりと草むらから出てきた。
A snake slithered out from the grass.
うどんがにゅるりと口の中に入っていった。
The udon noodle slipped into my mouth with a slurp.
Onomatopoeic or mimetic word; the sound-symbolic element にゅる suggests a slippery, wriggling motion.