vt to make torpid; to benumb.
2. stiffen ·vi to become stiff or stiffer, in any sense of the adjective.
3. stiffen ·vt to make stiff; to make less pliant or flexible; as, to stiffen cloth with starch.
4. stiffen ·vt to inspissate; to make more thick or viscous; as, to stiffen paste.