What is the meaning of Eccentricity?

The quality of being eccentric or odd; any eccentric behaviour.

The ratio, constant for any particular conic section, of the distance of a point from the focus to its distance from the directrix.

The eccentricity of the conic section (usually an ellipse) defined by the orbit of a given object around a reference object (such as that of a planet around the sun).

The farthest distance from a vertex to any other vertex.

Source: wiktionary.org