When used as a noun the term "cross" refers to trees that are grown from seed produced when both parents are known. Geneticists make controlled-crosses to improve the production characteristics of trees. This is done by shielding the female flower from random pollination, collecting pollen from the desired source tree, and carefully applying it to the female flower when it is receptive.
Question answered by Dr. Randy Sanderlin, Pecan Research-Extension Station plant pathologist.