ablation vs eating away

ablation and eating away both are nouns.

Word	Noun	Adjective	Verb	Adverb
ablation	Yes	No	No	No
eating away	Yes	No	No	No

As nouns, eating away is a hypernym of ablation; that is, eating away is a word with a broader meaning than ablation:

ablation: the erosive process that reduces the size of glaciers
eating away: (geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively

Other hypernyms of ablation include eroding, erosion, wearing, wearing away.

ablation (noun)	eating away (noun)
surgical removal of a body part or tissue	(geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively
the erosive process that reduces the size of glaciers