Code coverage means, how well your test set is covering your source code. i.e. to what extent is the source code covered by the set of Test cases. As mentioned in above answers, there are various coverage criteria, like paths, conditions, functions, statements, etc.
Chiasmus. Definition: Chiasmus is a specific type of parallelism. It consists of two parallel phrases in which corresponding words or phrases are placed in the opposite order.
During the diplotene stage: Within each tetrad, each pair of sister chromatids begins to separate. However, one or more ares remain in contact where chromatids are intertwined. Each such area, called a chiasma (pl. chiasmata) is thought to represent a point where nonsister chromatids have undergone crossing over.