Final answer:
A Torus palatinus is a fleshy immobile mass on the midline hard palate that is a benign bony growth.
Step-by-step explanation:
The fleshy immobile mass on the midline hard palate described in the question is most likely a Torus palatinus. Torus palatinus is a benign bony growth that appears as a protuberance on the midline of the hard palate. It is a common variation of normal anatomy and does not cause any functional problems or require treatment.