a. (Chem.) Of or pertaining to thallium; derived from, or containing, thallium; specifically, designating those compounds in which the element has a higher valence as contrasted with the thallous compounds; as, thallic oxide. [ 1913 Webster ]
(n) (psychoanalysis) the third stage in a child's development when awareness of and manipulation of the genitals is supposed to be a primary source of pleasure, Syn. phallic phase