The act of transitioning from a typical state of mind to one of a drug-induced state of mental fatigue where it becomes difficult to follow a train of thought or converse logically with others, without arousing suspicion
Pardon, Mortimer, have you noticed Nathaniel straight slipping today? The word on the street is that he has been up for two weeks on ice.
"Tommy's usually on point but he got caught slipping last Friday outside the McDonald's because he got distracted by Denise's fine ass. Took two in the chest before he could even get out his piece."
"Fool got jacked at the gas station. Homie was totally slipping: didn't even see dude coming."