"Hello" as a verb

A dictionary says that Hello could be a verb, noun and interjection. I'm not sure I saw it to be a verb though.

Q: Could someone provide an example of 'hello' where it's used as verb. In the meaning of its synonym phrase 'say hello'.

Can I say for example: "I hello you?" (Probably not but what can I hello?)

Theoretically, any, absolutely any word in English can be used as a verb. Nothing prevents you from helloing, betweening, egadsing or greating.

However, it's one thing to just use a word as a verb, but a different thing altogether to have it also be understood by others, and it's a different thing still for it to also be perfectly natural and unexceptionable. That is what language is all about, after all: communication. And as Calvin of Calvin and Hobbes famously put it, "verbing weirds language".

So yes, "I hello you" is a perfectly grammatical English sentence, but it is also a perfectly unidiomatic one. Perhaps not quite as nonsensical as the textbook example "colorless green ideas sleep furiously" — but at best, you might get away with it as a joke, or an otherwise deliberate attempt at unusualness, and at worst, people will just think you are a non-native speaker who could use better command of the language.

A native speaker is much more likely to produce "I greet you". Though that one has problems of its own, so actually just the greeting itself — "hello", or "greetings", or "welcome", or "top of the morning to you", or what have you — would be more common still.

Other answers have argued for hello's capacity to be a verb (but seem to doubt that it actually is a verb). I'll leave them the theory, here are recent examples of its use.

Stein had walked nodding and helloing straight to the bar and leaning on its structure of crates ordered a drink. (Thin Red Line)

He was just helloing me like I was his long-lost tich uncle. (Hockey Sur Glace)

I helloed to the boys to circle around on the other side of the canyon. (Wells, Fargo and Co Stagecoach and Robberies)

Walter helloed again, slammed the door to his truck and leaned against it. (The Coldest Night)

It seems to be especially common in poetry and westerns

You can greet someone; you can bid someone hello; you can acknowledge someone.

You are correct that the dictionary lists hello as a verb:

verb: hello; 3rd person present: helloes; past tense: helloed; past participle: helloed; gerund or present participle: helloing; verb: hallo; 3rd person present: halloes; past tense: halloed; past participle: halloed; gerund or present participle: halloing; verb: hullo; 3rd person present: hulloes; past tense: hulloed; past participle: hulloed; gerund or present participle: hulloing
1. say or shout “hello”; greet someone.

but I would say this would be strange in AmE.

Almost any word can be a verb. Probably the best examples to demonstrate this are expressions to express intoxication:

I was hammered
I got absolutely roof-topped

Or, to some examples of a British stand-up comedian:

I got utterly gazebo-ed, Completely bungalowed

Yes, you can indeed get "so ladle'd" and provided you say it in the right way (hint: emphasize the past participle), everyone will know what you're on about. Be careful, though, because some nouns have a rather specific, and sometimes deviant meaning when used as a verb (Teabag, scissor, spoon...)

I can imagine my using hello as a verb in certain cases, to convey a certain image/feeling:

All he did was helloing the guests, but refused to lend a helping hand.

Or, if I were to tell you of some formal happening where I felt as the odd one out, I might say something like

I helloed a couple of people, but I felt like a right git doing so

With this, I'd hope to conjure up an image of me, standing in a corridor, with a rented tuxedo that doesn't quite fit, being nervous and hoping to be able to sneak out ASAP.

However, I'd say "hello" is quite commonly used as a gerund, which is a verb used as a noun.
So you might think of the following sentence as a word, commonly used as a noun, being used as a verb, that is in turn being used as a noun again:

Your helloing everyone was a sight to behold

Then again, you're more likely to say:

[You] saying your hellos was a sight to behold

It is more likely used in the past tense, in the sense of greeting, wishing, hailing or just plain interrupting someone (esp., in the passing), analogous to Hi'ed (informal/ teen lingo). ="said 'Hello'".

TFD

intr.v. hel·loed, hel·lo·ing, hel·loes
To call "hello."

DRC

verb (used without object), hel·loed, hel·lo·ing.
5. to say “hello”; to cry or shout: I helloed, but no one answered.

Some related quotes appear in the answer by user @Unrelated on this page!