The Bilateral Symmetry ClipArt gallery includes 4 examples where one half is a mirror image of the other half. Other terms for this are: reflection symmetry, mirror symmetry, or mirror-image symmetry.
Letter A with a dotted vertical line that is a line of symmetry.
Letter B with a dotted horizontal line that is a line of symmetry.
Oval with dotted vertical and horizontal lines that are lines of symmetry.