A plastic spout (150,170) which is adapted to be sealed between two foil walls of a pouch. The spout has a spout body, which forms a passage (153) for delivering a medium from the pouch and/or feeding a medium to the pouch. In a bottom part thereof, the spout, on opposite sides, forms a sealing zone for a sealed connection to an adjoining foil wall. The sealing zones of the spout body are formed by sealing walls (158,159) which project downward from the spout body, each having a curvature over their entire length, such that each sealing wall is outwardly convex over its entire length with respect to an imaginary plane passing through the outermost ends, which adjoin one another, of the sealing walls. The sealing walls can preferably move flexibly transversely with respect to their plane and, on their inner side, are unsupported or are supported by one or more flexible supporting parts of the spout body.