vanishing point

noun

1. a point of disappearance, cessation, or extinction: His patience had reached the vanishing point.
2. (in the study of perspective in art) that point toward which receding parallel lines appear to converge.

noun

1. the point to which parallel lines appear to converge in the rendering of perspective, usually on the horizon
2. a point in space or time at or beyond which something disappears or ceases to exist