adjective: (genetics) Involving crosses between several or all possible combinations.
adjective: (obsolete) Of lines: Meeting and intersecting; not parallel.
noun: A set of all possible pairs of items from a specified set of items, especially when used for a study of diallel crosses.
noun: A form of logical fallacy in which a proposition that is required to prove another proposition can only be proved by means of assuming the truth of the proposition one is trying to prove; circular reasoning.