"Twinning" is a jargon term in motion pictures for various special effects that allow to double (or multiply) the presence of the same actor or actress on screen;
"Twinning" is a jargon term in animation when two parts on opposite sides of a character's body are moving the same way.
"Twinning" is a concept in education in Malaysia, where private colleges offer programmes whereby the student does part of his degree course locally and part of it in an overseas institution tied to the college.