Definitions

1. adjective

having or characterized by the most advanced stage of dry, hardened, outer layer or surface

“The crustiest part of the pizza was inedible.”

2. adjective

extremely old or out-of-date

“The crustiest old car in the neighborhood was a 1923 Model T.”

3. noun

the crustiest part of something

“The crustiest bit of the pie was at the edge.”

4. noun

the most hardened or difficult person

“He’s the crustiest guy in the company.”