an area of thick, hardened skin

accustom

(to cause blood etc) to become stiff or solid

coagulate

solid and firm; not easy to bend, dent, cut etc

rocklike

(to cause something) to become solid; (to cause a person) to become confident and determined

make or become solid

stubborn

pig-headed, stubborn

(to cause something) to become hard like bone; change into bone; (to cause a person) to become rigid in one's opinions

become hard from aging

(of concrete) in blocks ready for use in building

hardened

not easily bent or changed in shape; hard to stir, work, move etc; formal, unfriendly; thoroughly; a dead body

hard, inflexible