I tried looking up Sustainability on Dictionary.com and indeed, a lovely Prius ad was served. Other words that served a Prius 3rd Generation Solar Roof ad included “Solar Power”, “Green”, “Moonroof”, “Hybrid” and “Hybrid Car”.
Oddly, when I looked up “Prius” (definition: “Before; former”), the ad was not served. Iiiiiinteresting.
To read more, check out this All Thing’s Digital article, entitled Prius Takes Over Dictionary.com’s Home Page.