That which stands in the way, or opposes; anything that hinders progress; a hindrance; an obstruction, physical or moral.
All fixed (whether temporary or permanent) and mobile objects, or parts thereof, that are located on an area intended for the surface movement of aircraft or that extend above a defined surface intended to protect aircraft in flight. abbreviation: OBST also called: obstruction Fr: obstacle
Obstruction or hindrance that interrupts dog's scenting. May be natural or man-made and dog and/or handler may have to go around, over or through it. (Ganz & Boyd)