Slang definitions & phrases for speak the same language
speak someone's language
To understand one another very well, agree with each other
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with speak the same language
Understand one another very well, agree with each other, as in Negotiations went on for days, but finally both sides realized they weren't speaking the same language. This term, alluding to literal understanding of spoken words, dates from the late 1800s.