Dictionary.com
definitions

posthypnotic suggestion

noun
  1. a suggestion made to the subject while in a hypnotic trance, to be acted upon at some time after emerging from the trance
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
posthypnotic suggestion in Medicine

posthypnotic suggestion

n.
  1. A suggestion made to a hypnotized person that specifies an action to be performed after awakening, often in response to a cue.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.