The phrase "to hit the crossbar" means that in a sport like soccer or hockey, a player has kicked or shot the ball/puck in a way that it hits the horizontal bar (crossbar) that connects the goalposts, but does not go into the goal. Full definition
If either side hit the crossbar in the Tottenham v Chelsea match, Boylesports will double winnings on all markets! (football-bookmakers.com)
Coutinho made it 2 following a strong start to the second half from the Reds, with a composed drive into the bottom left corner after Wijnaldum hit the crossbar with a volley. (anfieldindex.com)
Moments later Munster hit the crossbar from a direct free kick. (wiganathletic.com)