|the movement or path of the earth or a heavenly body turning on its axis|
|any of the nine large heavenly bodies revolving about the sun and shining by reflected light: a similar body revolving about a star other than the sun|
|1.||the act of going or coming in; an entering|
|2.||a way in; entrance|
|3.||the right or permission to enter|
|4.||astronomy another name for immersion|
|[C15: from Latin ingressus, from ingredī to go in, from gradī to step, go]|
in astronomy, the apparent entrance of a smaller body upon the disk of a larger one as the smaller passes between the larger and the observer-e.g., the entrance of a satellite or its shadow on the disk of a planet. The term is also applied to the Moon's entrance into the Earth's shadow at the start of a lunar eclipse and to the Sun's entrance into a zodiacal constellation.
Learn more about ingress with a free trial on Britannica.com.