point d'appui

noun5

1. •
   An advantageous defensive support; a foothold.
2. •
   An anchor point against which one pushes.

   • The point d'appui of this lever is the pin to which it is attached; the moving power is the rower; and the resistance is the fluid; which is, however, contrary to the opinion of some writers. — 1842
3. •
   A given point or body upon which troops are formed, or by which they are marched in line or column.

   • Marched from the left, and to deployer to the left.—In which case the right squadron moves streight forward to the point d'appui marked by the Quarter Master, &c. &c. — 1795
4. •
   A specific note, chord, or phrase that serves as a stable reference point within a piece of music, providing harmonic or melodic grounding.

   • Any note belonging to these forms a point d'appui, which may be used mentally to pass to any note standing in a simple relation to the point d'appui. — 1878
5. •
   A focal point; a centre of attention.

   • Get a point d'appui from which to make your approaches, bring out the key-note to which the strained heart-chords shall respond in harmonious echo, and the battle is half won. — 1871