From WordNet (r) 3.0 (2006) [wn]:
crumbly
adj 1: easily broken into small fragments or reduced to powder;
"friable sandstone"; "friable carcinomatous tissue";
"friable curds formed in the stomach";"crumbly cookies"
[syn: crumbly, friable]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Crumbly \Crum"bly\ (-bl[y^]), a.
Easily crumbled; friable; brittle. "The crumbly soil."
--Hawthorne.
Syn: crimp.
[1913 Webster]