Soft and easily compressible; having a tendency to be squeezed or pressed into different shapes.
From the imitative word 'squish' (to make a soft crushing sound), with the '-y' suffix added to make an adjective. The word is relatively modern, appearing more frequently in casual English.
The word 'squishy' is one of the few English words that sounds like what it means—say it out loud and your mouth actually makes a soft, compressed shape, mirroring the physical quality you're describing.
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