Funnel trachea is a colloquialism for a congenital long-segment intrathoracic tracheal stenosis.
The diameter of the trachea immediately below the cricoid is normal, and becomes progressively more stenotic caudally. The posterior, membranous portion of the trachea may be partially or completely absent. In the latter case, the tracheal cartilage takes on a ring-like form.
The trachea is normally funnel-shaped in the neonatal period.