The coral turns white when it expels the minute organisms that live within its hard limestone core.

ECONOMIST: Pink coral into grey rubble

When workplace conduct is bad for business, business expels the bad apple, or sends him (or her) to an anger management class.

FORBES: New York Anti-Bullying Law A Big Bad Idea

It has a bivalve shell, two strings which move the valves against one another, and a small pump that expels water (he is still working on the best design for the foot).

ECONOMIST: Robots

Libya occasionally expels African migrants.

ECONOMIST: Developing countries attract migrants too