To dissever is to separate or divide something. If you spend too much time staring at screens, you might want to dissever yourself from technology and go camping this weekend.
These days, the verb dissever is considered old-fashioned or primarily literary — you're more likely to use words like sever or detach. It can be useful if you need a more poetic way to talk about dividing things, though: "Don't go to Maine for the summer; I can't bear to dissever my heart from yours!" Dissever comes from a Latin root, separare, "to pull apart."