1. In the physics of waves, an antinode is a point, line, or surface in a standing wave where some characteristic of the wave field has maximum amplitude. A standing, or stationary, wave is one whose shape stays the same and that doesn't appear to move through a medium. It occurs when a traveling wave is reflected along its own path. Antinodes and nodes are separated by a quarter of a wavelength.
2. In celestial mechanics, an antinode is either of the two points on an orbit where a line in the orbit plane, perpendicular to the line of nodes, and passing through the focus, intersects the orbit.