Use 'squelch' to describe sounds that create a vivid picture of squishiness in the listener's mind. She dropped the tomato, and it squelched against the kitchen floor.
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Movement Associated
'Squelch' often implies movement through something that would resist, like mud or wet terrain. The dog's paws squelched in the sodden grass.
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Onomatopoeic Usage
The word 'squelch' is onomatopoeic, which means its pronunciation mimics the actual sound it describes. Every step I took, my shoes squelched loudly, echoing in the silence.