This is one of the most popular search questions about sustainability on the Web.
Globally there are over one million/month searches with 450,000 of them from the United States. There is no one definition although a popular one cited is the Brundtland Commission of the United Nations of March 20, 1987: “sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” As Wikipedia reports, "At the 2005 World Summit it was noted that this requires the reconciliation of environmental, social and economic demands - the "three pillars" of sustainability. Here on EarthSayers 
we express these three pillars as planet, people, and prosperity. We created a taxonomy or content map for the concept which you can use to find information and better understand the concept.

Curated by mokiethecat

Waking Up to Sustainability by John Elkington

The Natural Step and Sustainability Explained in Two Minutes

What's Your Vision for Sustainability by Nikos Avionas

To Hell with Sustainability by Colin Beavan

Going to the Heart of Sustainability with Ilarion Merculieff

What is Just Sustainability by Julian Agyeman

What is Sustainability? by Allison and Bud McGrath

Being Frugal: The Original Sustainability?

Definition of Sustainable Innovation, Elementary Style by Dassault Systems

What is Sustainability by Hunter Lovins

Consumer Awareness of Sustainability by People 4 Earth

Sustainability Has Many Definitions by Stuart Hart

Use of the Term, Sustainability by Larry Merculieff (Aleut)

Definition of Sustainability by RealEyes

Defining Sustainability - Business Insights by Dr. Karl-Henrick Robert

How to Save the World by Eero Paloheimo

Sustainability 101: Exponential Growth by Dr. Albert Bartlett

Definition of Sustainability by Corporations by Christoph Lueneburger

Just Imagine: Sustainability CNN Interview of Majora Carter