What is meditation?

Meditation is my most favourite thing!

But apart from that:

From Ani Tenzin Palmo, Reflections on a Mountain Lake: Teachings on Practical Buddhism:

'As we begin to develop awareness of the mind, the mind itself appears to divide into two. A new aspect of the mind arises. This is referred to variously as the witness, the seer, the knower, or the observer. It witnesses without judgment and without comment. Along with the arrival of the witness, a space appears within the mind. This enables us to see thoughts and emotions as mere thoughts and emotions, rather than as "me" and "mine". When the thoughts and emotions are no longer seen as "me" or "mine", we begin to have choices. Certain thoughts and emotions are helpful, so we encourage them. Others are not so helpful, so we just let them go. All the thoughts and emotions are recognized and accepted. Nothing is suppressed. But now we have a choice about how to react. We can give energy to the ones, which are useful and skillful and withdraw energy from those which are not.'

From Dzogchen Ponlop, Mind Beyond Death:

'We should think about how we can make the best use of our practice so that we get the most out of it in the short time we have in this life. We do not have the leisure of wasting our time here by delaying the benefits of our practice. We have to use these situations as effectively as we can.

Before you begin any practice, first think very carefully about your motivation. When we are engaged in the threefold process of study, contemplation and meditation, we should be very specific, very clear about why we are doing it. We should remind ourselves, "I am doing this to transcend my negative emotions and my ego-clinging." This is a general example of a specific intention. However, to be more precise, we need to consider the unique make-up of our own individual kleshas [intense states of suffering, and ignorance]. Once we have identified our strongest emotion, then we can focus on the practices that will alleviate it. We begin with whichever emotion is strongest for us and then we move on to the next strongest, followed by the next, and so on.

It is important for us to prioritize our practice in this way. We have to keep our intention very clear in all three phases--in our study, in our contemplation and in our meditation. During shamatha or other practices, when thoughts come up, we recall that our purpose is to overcome our disturbing emotions and kleshas. We have to have a sense of willpower or determination in our minds. In order for the remedy to work, we must tell ourselves, "Yes, I am going to transcend this anger. I am going to work with it." Otherwise, if we do not have a clear idea, if we simply sit there with an indefinite or vague intention, then the effect also will be vague. We may have sat for one hour and although that time will not have been wasted, because it was not directed in an intentional way, the experience will not be so sharp, to the point or effective.'

[This relates to the blog post Resolutions for contentment]

These quotes are from A view on Buddhism: Meditation practice

To be added to ... there will be more! If you have a great definition for meditation to share please please let me know.