toughen

1 to increase the ability of (as a muscle) to exert physical force weight lifting will help toughen those flabby muscles of yours Synonyms beef (up), fortify, harden, strengthenRelated Words anneal, temper; firm (up), tone (up); energize, invigorate, vitalize; restrengthenNear Antonyms cripple, incapacitate, paralyze; damage, harm, hurt, impair, injure; break down, wear out; sap, undercut, undermineAntonyms debilitate, enervate, enfeeble, weaken

2 to make able to withstand physical hardship, strain, or exposure hiking every morning through snow and ice toughened him considerably Synonyms fortify, indurate, inure, season, steel, strengthen, hardenRelated Words acclimate, acclimatize, adapt, adjust; anneal, temper; invigorate, vitalize; immunize; bolster, boost, brace, buttress, enforce, forearm, prop (up), reinforce (also reenforce), support; break in, limber (up), train; accustom, condition, habituate, naturalizeNear Antonyms emasculate, enervate, enfeeble, exhaust, sap, weaken; cripple, debilitate, hamstring, incapacitate; sensitizeAntonyms soften

3 to make more harsh, uncompromising, or severe attempts to toughen conditions under which waivers from military service would be permitted Synonyms harden, stiffen, strengthen, harshenNear Antonyms lessen, moderate, softenAntonyms ameliorate, ease