1. a box or receptacle containing loose sand especially a box that contains sand for children to play in

2. a place, area, or environment that provides opportunities for variation and experimentation in a way suggestive of children playing in a sandbox
The Suttle Lodge is not a full-service hotel. Instead, it is better thought of as a sandbox: it provides all the amenities for you to create your own ideal experience.
— Lance Richardson ; such as

3. a video game or part of a video game in which the player is not constrained to achieving specific goals and has a large degree of freedom to explore, interact with, or modify the game environment
… Untitled Goose Game is a sandbox in which objectives sometimes feel more like suggestions. I still want to get back in there and just mess with people more—see what happens when I get certain characters to chase me into certain areas, or if others will react to particular items.
— Nathan Grayson — often used before another noun
a sandbox gameVideo games played in sandbox mode, or purpose-built sandbox games, allow the player access to the whole world (the box) at once, and allow her to change that world at will (the sand). There is no preset narrative to force the player to run, hide, or shoot, and no marauders to destroy what she has built.
— Alexandra Lange

4. an isolated environment on an electronic device (such as a computer) within which applications cannot affect other programs or data on the device
Software development often occurs inside a sandbox, defined as a confined virtual environment in which one or several developers can freely and safely experiment with untested code and new technologies.
— Janine Gianfredi Businesses should add an application to their email systems that tags all emails containing a link or attachment. If an employee clicks on the link or attachment, the application launches it in a safe digital environment, called a sandbox, preventing any malicious application from infecting the employee's device or any others connected to it.
— Cameron G. Shilling

5. a controlled environment supervised by a regulatory authority within which existing regulations are relaxed or removed to allow businesses to more freely experiment with new products and services
The sandbox enables the development of telemedicine services with close monitoring of all aspects of safety, including clinical processes, medication delivery and data protection, while co-creating the appropriate regulations.
— Raymond Chua Other efforts of Carolina Fintech Hub include finding ways to leverage the local supplies of venture capital and corporate capital to help good ideas grow. The organization is working with the North Carolina General Assembly members to bring forth a first-of-its-kind fintech sandbox, which would create a business-friendly environment for fintech startup activity.
— Charlotte Business Journal (North Carolina)

6. a low box filled with sand that children can play in

7. a large low box for holding sand especially for children to play in