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.
Definition. In rhetoric, chiasmus is a verbal pattern (a type of antithesis) in which the second half of an expression is balanced against the first with the parts reversed. Essentially the same as antimetabole.