To break, or cause something to break, into small pieces. (Cambridge Dictionary)
To become weaker in strength or influence. (Cambridge Dictionary)
If something crumbles, or if you crumble it, it breaks into a lot of small pieces. (Collins Dictionary)
If an old building or piece of land is crumbling, parts of it keep breaking off. (Collins Dictionary)
If something such as a system, relationship, or hope crumbles, it comes to an end.
Break or fall apart into small fragments, especially as part of a process of deterioration. (Oxford Dictionaries)
Crisp or crumble? Baked summer desserts defined.
Dream Of Teeth Crumbling. What does crumbling teeth mean in a dream?
Pensioner, 75, who shares £ 1m new-build home with Alzheimer’s suffering wife fears it is CRUMBLING – as dozens claim houses have weak mortar.