sandbox

Short definition from Wiktionary

Noun

1. 1
   A children's play area consisting of a box filled with sand.
2. 2
   A box filled with sand that is shaped to form a mould for metal casting.
3. 3
   A container for sand or pounce, used historically before blotting paper.
4. 4
   An animal's litter box.
5. 5
   A box carried on locomotives, from which sand runs onto the rails in front of the driving wheels, to prevent slipping.
6. 6
   An isolated area where a program can be executed with a restricted portion of the resources available.
7. 7
   A page on a wiki where users are free to experiment without destroying or damaging any legitimate content.
8. 8
   The Middle East.

Verb

1. 1
   To restrict (a program, etc.) by placing it in a sandbox.
2. 2
   To brainstorm; to prototype.