When thinking about sustainability, the three pillars of sustainability come to mind: social, environmental, and economic. Environmental sustainability in buildings is primarily concerned with sourcing of materials, energy efficiency, and water reduction and reuse to name a few. Examples of social sustainability in buildings could be ethical sourcing of materials, encouraging active lifestyles by placement of staircases/bike racks, and accessibility of building features to those with disabilities. Lastly, economic sustainability might include thinking about the building lifespan and the cost of heating/cooling.
More abstractly, sustainability to me means self-sufficient and lasting. Thinking about building design, having long lasting structures that are able to (at least mostly) sustain themselves is an embodiment of the phrase sustainable design.
Passive design is particularly interesting to me in building development, as it harnesses already available resources to drive processes within the structure and reduce loads. Orientation of the building, strategic placement of overhangs and windows, facade materials, and high R-value insulation are key. An example of a building that utilizes many passive design features is the Bulitt Center is Seattle which is Net Zero Energy and Net Zero Water.
Water collection and water reuse are also components of sustainable design that are advantageous to consider. In terms of materials, wood is a durable and sustainable source due to the fact that it can be regrown and harvested. An example of a building that uses wood as its frame is the T3 MINNEAPOLIS building, in which the majority was lumber from trees killed by the mountain pine beetle.
http://mg-architecture.ca/work/t3-minneapolis/
The new high-rise buildings at Stanford, EVGR (Escondido Village Graduate Residences) have features within the building that promote sustainability, including having accessible sorting stations for compost, recycling, and trash.