ぐんにゃり

also: ぐんなり

ぐ

ん

にゃ

り

Meanings

adverb taking the 'to' particle, adverb, noun or participle which takes 'suru'

limp; listless; drained of energy

onomatopoeic or mimetic word

Describes a person or animal that is physically or mentally exhausted, lacking strength or motivation, often in a slumped or drooping posture.

彼かれは疲つかれてぐんにゃりとソファに沈しずみ込こんだ。

Exhausted, he sank limply into the sofa.

adverb taking the 'to' particle, adverb, noun or participle which takes 'suru'

flaccid; wilting; soft and shapeless

onomatopoeic or mimetic word

Used for objects, especially food or plants, that have lost firmness and become limp or soggy.

このきゅうりは冷れい蔵ぞう庫こに入いれすぎてぐんにゃりしている。
This cucumber has gone limp from being in the fridge too long.
花はなが水みず不ぶ足そくでぐんにゃりとしおれている。
The flowers are wilting limply from lack of water.

ぐったり
ぐったり emphasizes complete exhaustion or limpness, often of a person or animal, while ぐんにゃり can also describe objects that have lost firmness.
へなへな
へなへな suggests weakness or lack of strength, often with a sense of flimsiness, whereas ぐんにゃり focuses on limpness and loss of shape.

Mimetic word; the exact origin is uncertain, but the sound ぐんにゃり evokes a sense of softness and limpness.