Ap·pui n.
 1. A support or supporter; a stay; a prop. [Obs.]
    If a vine be to climb trees that are of any great height, there would be stays and appuies set to it.   --Holland.
 2. Man. The mutual bearing or support of the hand of the rider and the mouth of the horse through the bit and bridle.
 Point d'appui  Mil. (a) A given point or body, upon which troops are formed, or by which are marched in line or column. (b) An advantageous defensive support, as a castle, morass, wood, declivity, etc. (c) any point of support or basis of operations, as a rallying point.

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