be on to


Be aware of or have information about, as in They can't pull that trick again; we're on to them now. [Colloquial; second half of 1800s]

Words Nearby be on to

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.