Growing a weed

I was curious about the expression I often see on some gardening forum  - "grows like a weed".

What is a weed? Wikipedia says "A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-made settings.... More specifically, the term is often used to describe native or nonnative plants that grow and reproduce aggressively."

I was curious so I decided I would try to grow a weed. Or at least I think I did grow a weed.

A plant I bought from the nursery had a big mysterious looking plant growing in it. I removed it from the pot and grew it in a separate pot.

The plant did grow very agressively! In about 3 weeks, it doubled in size, produced tiny purple flowers that dried up and became seed-like things. And apart from that, new shoots sprouted out from the sides of the plant. And I didn't really give it anything about from a pot and the occassional watering.

So there you go. Wikipedia is right - a weed is a plant that grows and reproduce aggressively.

P/S: My experiment has ended and I have very cruelly cut down this plant.