verb (used with or without object), re-upped, re-up·ping. Military Informal.

to reenlist.

Origin of re-up

An Americanism dating back to 1905–10 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Word Origin and History for re-up

"to re-enlist," 1906, U.S. armed forces slang, from re- "back, again" + up (v.) "enlist." Related: Re-upped; re-upping.

Online Etymology Dictionary, © 2010 Douglas Harper