WordNet sense 1 (made tough by habitual exposure):

inured, enured

WordNet sense 2 (physically toughened):

tough, toughened

WordNet sense 3 (made hard or flexible or resilient especially by heat treatment):

tempered, treated

WordNet sense 4 (used of persons; emotionally hardened):

hard-boiled, case-hardened

WordNet sense 5 (dispassionate):

hard

WordNet sense 6 (converted to solid form (as concrete)):

set