American Heritage Dictionary
(1)
Century Dictionary
GNU Webster's 1913
WordNet
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Elsewhere on the web
A vertical-takeoff aircraft, like the hummingbird, has a very high metabolism, which means it requires a lot of energy.— Paul Moller on the Skycar

Bubble size: how much this word was used in a year
Bubble height: used more or less than expected, vs. all uses evenly distributed
You can expect to see this word a few times a year.