One who does not respond to external stimuli, for example through the senses. You could shoot a catatonic in the foot and they would not notice.
Very few people can ever achieve complete catatonic status. Those who do rarely recover, resulting in pain and untold suffering for the victim's family.
when ur in math class and u start spacing out so hard that nothing that happens around you is registered. you start drooling, and mumbling to ur self while you sit there not moving a muscle wishing there was a fire drill today. you want to fall asleep but you know that asshole that calls himself a "teacher" will wake ur dumbass up. so u just sit there lookin' like Donny Darko spacing out.
"bro during mr. bobs math class i space out so hard sometimes i fall asleep with my eyes open."
"math class catatonia man, happens to the best of us."