Soft and fat. (Cambridge Dictionary)
Hanging loosely or limply, as flesh or muscles; flaccid. (Dictionary.com)
Having such flesh. (Dictionary.com)
Lacking strength or determination. (Dictionary.com)
Lacking resilience or firmness: Flaccid. (Merriam – Webster)
Weak and ineffective: Feeble. (Merriam – Webster)
Ten Best Home Exercises To Get Rid Of Flabby Arms.
Flabby skin after weight loss, 7 tips.