"crustiest" in the adjective sense
1. crusted, encrusted, crusty, crustlike
having a hardened crust as a covering
2. crusty, curmudgeonly, gruff, ill-humored, ill-humoured
brusque and surly and forbidding
"crusty remarks"
"a crusty old man"
"his curmudgeonly temper"
"gruff manner"
"a gruff reply"
Source: WordNet® (An amazing lexical database of English)
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