(1):

(n.) Power or liberty of entrance or access; means of entering; as, all ingress was prohibited.

(2):

(n.) The entrance of the moon into the shadow of the earth in eclipses, the sun's entrance into a sign, etc.

(3):

(v. i.) To go in; to enter.

(4):

(n.) The act of entering; entrance; as, the ingress of air into the lungs.