The Collaborative International Dictionary of English v.0.48:
Upstroke \Up"stroke`\, n.
An upward stroke, especially the stroke, or line, made by a
writing instrument when moving upward, or from the body of
the writer, or a line corresponding to the part of a letter
Some upstroke of an Alpha and Omega. --Mrs.
WordNet (r) 3.0 (2006):
n 1: a stroke normally made in an upward direction