is it a motorcycle?

just came upon an interesting question based on a vehicle spotted by member M'Lady. what constitutes a motorcycle?

wikipedia: a two or three wheeled motor vehicle.
webster's: a vehicle with two wheels that is powered by a motor and that can carry one or two people

they can't even agree on how many wheels! there's got to be a more defining method. so i'm gonna throw a series of pictures at you and you tell me which you think should be considered motorcycles. add more for consideration as you see fit. i've got some ideas to amend this definition but i want to see some debate first.

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