stiff·en 
/ˈstɪfən/ verb
stiff·ens; stiff·ened; stiff·en·ing /ˈstɪfən/ verb 1 [no obj] : to stop moving and become completely still especially because of fear, anger, etc.
▪ She stiffened when he grabbed her shoulder. ▪ The dogs stiffened in alarm. 2 [no obj] : to become painful to move or use — often + up ▪ My muscles stiffened up the next day. 3 : to become more severe or strong or to make (something) more severe or strong [no obj] ▪ The wind stiffened. ▪ His resolve has stiffened. [+ obj] ▪ He stiffened his resolve. ▪ The law would stiffen penalties for tax evasion. 4 [+ obj] : to make (something, such as cloth) difficult to bend or move
▪ stiffen a shirt with starch
▪ She stiffened when he grabbed her shoulder. ▪ The dogs stiffened in alarm.
▪ stiffen a shirt with starch
— stiff·en·er /ˈstɪfənɚ/ noun, plural stiff·en·ers [count]
/ˈstɪfənɚ/ noun, plural stiff·en·ers [count]
