I am not an expert, but my understanding is that 'bhāvanā' basically means something like "causing to become or develop". In the context of spiritual practice it can mean something like "developing a mental state or mood", basically working with one's mind for a spiritual purpose, so, very similar to how 'meditation' and 'cultivation' are used in English now: http://en.wikipedia.org/wiki/Bhavana
I don't know if 'abhāvanā' was ever actually used in India, but I think it makes good sense as a back translation from Tibetan. If the OP was not about the Tibetan term 'sgom med', then all bets are off.
The thousands of lines of the Prajnaparamita can be summed up in the following two sentences:
1) One should become a Bodhisattva (or, Buddha-to-be), i.e. one who is content with nothing less than all-knowledge attained through the perfection of wisdom for the sake of all beings.
2) There is no such thing as a Bodhisattva, or as all-knowledge, or as a ‘being’, or as the perfection of wisdom, or as an attainment.
To accept both these contradictory facts is to be perfect. - Conze