Is the word "bonsai" used both as a noun and a verb?

Is it common to use the word "bonsai" as a verb as in the following passage? And what does it mean?

If you've ever crammed into the back of a Toyota with one or more males over the age of seven, you're likely familiar with the phenomenon recently popularized as manspreading.

A target of women's websites and public transit authorities, the practice involves the widening of a man's legs while seated such that those adjacent must bonsai themselves into what little sittable space remains in a bus or airplane row.

Source: "The manspreading epidemic: Is it really an epidemic?", CNN

Solution 1:

Yes, it can be used as a verb and CNN used it that way.

Verbification in English is common and the linked Wikipedia article explains there are thousands of them:

Examples of verbification in the English language number in the thousands, including some of the most common words such as mail and e-mail, strike, talk, salt, pepper, switch, bed, sleep, ship, train, stop, drink, cup, lure, mutter, dress, dizzy, divorce, fool, merge, to be found on virtually every page in the dictionary. Thus, verbification is by no means confined to slang and has furnished English with countless new expressions: "access", as in "access the file", which was previously only a noun, as in "gain access to the file". Similar mainstream examples include "host", as in "host a party", and "chair", as in "chair the meeting". Other formations, such as "gift", are less widespread but nevertheless mainstream.

When a noun like 'bonsai' is used in the linked article, there is no doubt that it is used as a verb as it follows the modal verb must and you should use a verb before the reflexive pronoun themselves to make sense.

The noun 'bonsai' comes from the Japanese noun ' 盆栽 ぼんさい' and it means

a tree or shrub that has been dwarfed, as by pruning the roots and pinching, and is grown in a pot or other container and trained to produce a desired shape or effect.

[Dictionary.com]

...Those adjacent must bonsai themselves into what little sittable space...

could be rephrased to

...those adjacent must cram themselves into what little sittable space...

Related question: “To science the sh*t out of something”

Solution 2:

Officially it is a noun. The word comes from the combination of two Japanese words:

“Bon” is a dish or thin bowl (“a modified vessel which has been divided or cut down from a deeper form”).

“Sai” is a tree or other growing plant which is planted – “planted,” as would be a halberd or spear or pike stuck into the ground.

“Bonsai” thus means or denotes “a tree which is planted in a shallow container".

-- Bonsai Empire

However the noun has unofficially been adopted for use as a verb (in much the same way that the verbs to hoover^[1] and to google have been adopted from the nouns and phrases to vacuum using a Hoover and to search using the Google search engine) to mean to make small like a bonsai.

The English language is littered with such noun-orientated phrases that have been shortened into a single verb using the noun as the new verb. Is it correct? It's evolution.

So in your quoted phrase, to bonsai oneself would be to make oneself small like a bonsai to fit into a small space (like a Bon) caused by the "manspreading".