What is a "carnivorous plant?

This may seem a simple question, but it is actually a matter of some discussion and disagreement. The following is, I believe, the most straightforward and sensible definition, as I wrote it myself (Rice 2010a, 2011b)!

A plant is carnivorous if it has the following three attributes:

The plant must have clear adaptations to capture prey such as a trap. It can have extra features that help improve the trapping efficiency.
The plant has some way to digest the prey into a form that can be absorbed by the plant. The plant may produce digestive enzymes, or it may rely on bacteria or other organisms to perform the digestion for it.
The plant must have a way of absorbing the nutrients, and must benefit from the nutrients.
That is a slightly simplified version of my definition, but it notes the three important parts. In the next few FAQ pages I will provide details of each three steps.

Plants that have some, but not all, of the above attributes are called semi-carnivorous, para-carnivorous, or sub-carnivorous. (Avoid the word "proto-carnivorous", as we can't say that evolution is moving in some particular direction---evolutionary forces can change at the drop of a hat.)

Source: http://www.sarracenia.com/faq.html