Design sprint

A design sprint is a time-constrained, five-phase process that uses design thinking with the aim of reducing the risk when bringing a new product, service or a feature to the market. The process aims to help teams to clearly define goals, validating assumptions and deciding on a product roadmap before starting development. It seeks to address strategic issues using interdisciplinary, rapid prototyping, and usability testing. This design process is similar to Sprints in an Agile development cycle.
How it started.
In 2010, a handful of pioneers from different parts of the Google ecosystem—UX designers, engineers, researchers, and product managers—started looking for ways to break from the tyranny of back-to-back 30-minute meetings and the challenges of working cross-functionally. A few people who had been trained in IDEO's design thinking approach began experimenting, remixing different methods—user research, business strategy, and even psychology—into something that could supercharge their work on bold, never-been-done before projects.
Possible uses.
Claimed uses of the approach include
Phases.
The creators of the design sprint approach, recommend preparation by picking the proper team, environment, materials and tools working with six key 'ingredients'. 
Deliverables.
The main deliverables after the Design sprint:
Team.
The suggested ideal number of people involved in the sprint is 4-7 people and they include the facilitator, designer, a decision maker (often a CEO if the company is a startup), product manager, engineer and someone from companies core business departments (Marketing, Content, Operations, etc.).
Variants.
The concept sprint is a fast five-day process for cross-functional teams to brainstorm, define, and model new approaches to business issue.