tricuspid valve

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The three-segmented valve of the heart that keeps blood in the right ventricle from flowing back into the right atrium.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A heart valve with three cusps which prevents backflow of blood from the right ventricle into the right atrium.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun valve with three cusps; situated between the right atrium and the right ventricle; allows blood to pass from atrium to ventricle and closes to prevent backflow when the ventricle contracts