Betray, double-cross, cheat, as in Jack crossed up his buddies and told the police they had broken in. Originally this usage often was put simply as to cross. [Early 1800s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use cross up in a sentence
I shall keep these beautiful glass beads always, and put the cross up over my dressing-table.Betty's Bright Idea; Deacon Pitkin's Farm; and The First Christmas of New England | Harriet Beecher Stowe
Sometimes it was rough work, with so many creeks to cross up to our middles, and sometimes our necks, in mud and water.
"If the fox comes back," said my companion, "he will cross up there or down here," indicating two points not twenty rods asunder.In the Catskills | John Burroughs
If we cross up with a bunch of Cheyennes, there may be trouble.The Sunset Trail | Alfred Henry Lewis
First cross up the world by getting a weapon with no defense.Cue for Quiet | Thomas L. Sherred