the GNU version of the Collaborative International Dictionary of English
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 thus made.
The Century Dictionary and Cyclopedia
n. In mech., the traverse of a piston, or of any reciprocating or rocking element of an engine or machine, in which the driving element is moving upward, or the principal driven element is coming up.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a stroke normally made in an upward direction
Word Usage
"Their ghostly appearance is enhanced by the fact that the undersides of their chalk-white wings are dark brown, so with every upstroke they seem to disappear in the moonlight, then reappear on the downstroke."