high-five (hī'fīv') n.
Slang A gesture of greeting, elation, or victory in which one person slaps an upraised palm against that of another person. high'-five' v.
originally U.S. basketball slang, 1980 as a noun, 1981 as a verb, though the greeting itself seems to be older (e.g. Dick Shawn in "The Producers," 1968).