harden (v.)

• acclimate
• acclimatize
• accommodate
• accustom
• adapt
• adjust
• anneal
• brace
• break
• brutalize
• buttress
• cake
• calcify
• callous
• compact
• concrete
• condition
• confirm
• conform
• congeal
• consolidate
• crystallize
• domesticate
• domesticize
• dry
• endure
• establish
• familiarize
• firm
• fix
• fortify
• fossilize
• freeze
• gentle
• gird
• habituate
• housebreak
• indurate
• intensify
• inure
• invigorate
• lapidify
• naturalize
• nerve
• orient
• orientate
• ossify
• petrify
• prop
• refresh
• reinforce
• reinvigorate
• restrengthen
• season
• set
• solidify
• steel
• stiffen
• strengthen
• support
• sustain
• tame
• temper
• toughen
• train
• undergird
• vitrify