upstroke

The parts are in correct mechanical balance because two pistons are on the upstroke while the other two are descending.
Aviation Engines|Victor Wilfred Pag
This is characterized by a long sweeping upstroke, and the recurving downstroke cuts the staff about in half.
Warren Commission (7 of 26): Hearings Vol. VII (of 15)|The President's Commission on the Assassination of President Kennedy
During the upstroke the cup collapses inwards and allows air to pass by it.
How it Works|Archibald Williams
After the downstroke is completed, the teeth A will cut on the upstroke, the teeth B cutting on the downstroke, etc.
The Boy Mechanic, Book 2|Various

During an upstroke this closes, and the other opens; the reverse happening during a downstroke.
How it Works|Archibald Williams

British Dictionary definitions for upstroke

upstroke

/ (ˈʌpˌstrəʊk) /

noun

an upward stroke or movement, as of a pen or brush
the mark produced by such a stroke

the upward movement of a piston in a reciprocating engine

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012