What is a weed?

I have a gardener to cut my grass and hedges. He always asks if I want weedkiller using. I say I do not have any weeds, just wild flowers. He's only been doing it for a year, so hopefully he'll get the message soon!

I like this quote:

But a weed is simply a plant that wants to grow where people want something else. In blaming nature, people mistake the culprit. Weeds are people's idea, not nature's. ~Author Unknown

And crowds out the flowers that aren't weeds!

A weed is all the above plus it grows profusely without any help or encouragement!

A weed is a plant that slugs and snails don't want to eat.

A Weed is a flower in the wrong place by Ian Emberson

A weed is a flower in the wrong place,
a flower is a weed in the right place,
if you were a weed in the right place
you would be a flower;
but seeing as you’re a weed in the wrong place
you’re only a weed –
its high time someone pulled you out.

I've always understood a weed to be a plant growing where you don't want it to be.
As you say it's subjective.

If a wild flower is where you don't want it, it's a weed.
If a weed is where you are happy to see it, it's a wild flower.