That cup of tea spilled. Verter VS tirar
I wanted to say a cup of tea spilled so I said "vertió un vaso de té" and the busgirl corrected me to "tiró un vaso de té".
He spilled a glass of tea. Please clean it up.
Vertió un vaso de té, favor de limpiarlo.
7 Answers
"Verter" does not necessarily have to be accidental: it can be done -and it often is- in a controlled manner, but as long as you let some liquid (or other similar stuff) fall, it is "verter", so I don't see the problem in using that verb in that sentence. "Derramar" is like "verter", but generally accidentally, and never in a controlled manner. "Tirar" is either purposefully or accidentally, and it can be a solid as well as a liquid, but it is meant to happen in a violent or an uncontrolled manner. In Spain, "verter" is less used colloquially, but it is definitely used nevertheless.
Hi Jeezle! Let me just complicate matters further. I'm not good at this, but I would have used "derramar". Like: Derramó una taza de té.
Let's see what the experts say!
You also have derramar. 
¡Qué bueno no había derramado/tirado la cerveza porque eso habría sido un desastre!
A cup of tea spilled = Una taza de té se derramó / se cayó (pronominal; intransitivo).
He spilled a glass of tea = Tiró un vaso de té.
I'm familiar with verter as to pour (something), or at least to transfer or "spill" liquid in a controlled manner.
you're spilling the milk - estás derramando la leche
you've spilled or spilt coffee on your shirt - te ha caído café en la camisa
However!
to spill the beans - descubrir el pastel, contarlo todo
"Verter" does not necessarily have to be accidental: it can be done -and it often is- in a controlled manner, but as long as you let some liquid (or other similar stuff) fall, it is "verter", so I don't see the problem in using that verb in that sentence. "Derramar" is like "verter", but generally accidentally, and never in a controlled manner. "Tirar" is either purposefully or accidentally, and it can be a solid as well as a liquid, but it is meant to happen in a violent or an uncontrolled manner. In Spain, "verter" is less used colloquially, but it is definitely used nevertheless
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Verter and derramar mean to spill or pour.
Tirar means to knock over, among other things.
