(1):

(n.) A concave cut made in the teeth of some saw blades.

(2):

(n.) The tube by which food and drink are carried from the pharynx to the stomach; the esophagus.

(3):

(n.) Something shaped like the food passage, or performing similar functions

(4):

(n.) A channel for water.

(5):

(n.) A preparatory cut or channel in excavations, of sufficient width for the passage of earth wagons.