1. Playground equipment, usually part of a jungle gym. Talented kids can swing on them like perfect little simians. Kids who can't are subject to ridicule.
2. Delicious after school snack made from former lab chimps.

Basicaly a ladder placed horizontally from 4-6 feet above the ground, supported by two legs at each end. As children are ment to hang from the crossbars, the rungs are usualy made from narrow metal pipes.
The goal is usualy to swing from one rung to the next, making it all the way across without touching the ground.

In modern playgrounds they are being replaced by a type of 'zip cord'--a handle that you hang from and jump towards the other side. The handle is mounted on ball bearings, and so you can cross the distance with minimal arm strength.

Piece of equipment used for physical fitness amongst children. They condition climbers in agility, upper body strength, confidence, spatial awareness and endurance, with children often competing how far they can cross without falling, or relying on the fewest rungs. Other uses include locking ones legs around the bars and swinging upside down. To prevent playground injuries, monkey bars are usually sited over a sand pit.

al-Qaeda makes good use of monkey bars in their terrorist training camps.