Talk:Archaeopteryx was probably not an ancestor of modern birds (Talk.Origins)

Meaning of transitional
1 a : passage from one state, stage, subject, or place to another : CHANGE b : a movement, development, or evolution from one form, stage, or style to another. PrometheusX303 20:42, 16 April 2006 (GMT)

And according to Wikipedia "A transitional fossil is the fossil remains of a creature that exhibits primitive (or "conservative") traits in comparison with the more derived life-forms to which it is related. "Missing link" is a popular term used for transitional forms. According to evolutionary theory, in which all populations of organisms are in transition, a "transitional form" is a human construct that vividly represents a particular evolutionary stage, as recognized in hindsight."

Evowiki: "A transitional fossil is a fossil which bridges two major taxonomic groups. According to the theory of evolution, new species arise as a consequence of new traits that appear in a lineage; if this theory is correct, any life-forms which exist in the middle of this process would be a sort of mosaic, combining old traits from the ancestral form with new traits that are not found in the ancestral form. In the context of biological science, therefore, the word "transitional" (as seen in the phrases "transitional fossil" or "transitional form") refers to precisely this sort of mosaic life-form."