To slouch, droop, or hunch forward or to one side. You need to stop slouching over like that while you work at the computer, or you'll give yourself major back pain down the line! Everyone in the meeting had started to slouch over, their eyes glossing over out of sheer boredom.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
[for someone] to collapse and fall over forward in a sitting position. Just after the gunshot, Bruno slumped over and slid from his chair.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.