Available Definitions:
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.