| Stiffen 1. (v. t.) To make stiff; to make less pliant or flexible; as, to stiffen cloth with starch. 2. (v. t.) To inspissate; to make more thick or viscous; as, to stiffen paste. 3. (v. t.) To make torpid; to benumb. 4. (v. i.) To become stiff or stiffer, in any sense of the adjective. Thesaurus Entries amplify, back, be tough, beef up, brace, brace up, buttress, case harden, charge, clot, coagulate, confirm, congeal, crystallize, electrify, endure, energize, fortify, galvanize, generate, gird, hang tough, harden, invigorate, jell, loop in, nerve, plug in, prop, refresh, reinforce, reinvigorate, restrengthen, rigidify, screw up, set, shock, shore up, short, short-circuit, solidify, steel, step down, step up, strengthen, support, sustain, switch off, switch on, tauten, temper, tense, thicken, tighten, toughen, trice up, turn off, turn on, undergird |