  In this paper, we give the notion of a CLWX 2-algebroid and show that a
QP-structure of degree 3 gives rise to a CLWX 2-algebroid. This is the higher
analogue of the result that a QP-structure of degree 2 gives rise to a Courant
algebroid. A CLWX 2-algebroid can also be viewed as a categorified Courant
algebroid. We show that one can obtain a Lie 3-algebra from a CLWX 2-algebroid.
Furthermore, CLWX 2-algebroids are constructed from split Lie 2-algebroids and
split Lie 2-bialgebroids.
