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.
Answer: A chiasm (also called a chiasmus) is a literary device in which a sequence of ideas is presented and then repeated in reverse order. The result is a mirror effect as the ideas are reflected back in a passage. Each idea is connected to its reflection by a repeated word, often in a related form.