1) Bisection 
In heraldry, dimidiation is a method of marshalling (heraldically combining) two coats of arms. For a time, dimidiation preceded the method known as impalement. Whereas impalement involves placing the whole of both coats of arms side by side in the same shield, dimidiation involves placing the dexter half of one coat of arms alongside the sinister...
• (n.) The act of dimidiating or halving; the state of being dimidiate.
The heraldic practice of combining two animals in a coat-of-arms into a single composite creature.
Di·mid`i·a'tion noun [ Latin dimidiatio .] The act of dimidiating or halving; the state of being dimidiate. 
dimidiation The act of having a division into two equal parts.