(intr) to become a member of a military or other organization; enlist
(often foll by with) to unite or connect
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
How to use join up in a sentence
Which is, Democratic operatives say, part of the reason to join up again.
He also may have tried to defect from the Taliban after they lost the war and join up with the Afghan government.CIA Chief, White House Chief of Staff Long Argued the Taliban 5 Could Go Free | Josh Rogin, Eli Lake | June 7, 2014 | THE DAILY BEAST
Kids who were 11 in 2003 are now old enough to join up and get killed in Iraq in a "non-combat capacity."
Yes to both, but then again, more importantly, why did Gregg agree to join up with the Obama administration to begin with?
Im going to join up with the Mounted, too, when we git back.The Radio Boys Rescue the Lost Alaska Expedition | Gerald Breckenridge
Penny felt the world fall still further apart when the man she had begun to trust said, "What if I join up with you?"The Lone Ranger Rides | Fran Striker
A man just under military age, with seven children, is ordered to join up.
If you join up two such coils as they are usually joined, in series, but without any iron yoke across the cores, the throw was 17.
join up the two sides, leaving an opening at the top, and finish with two bars and a gold chain.My Knitting Book | Miss Lambert