How do you spell Stiffen

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.