Psyche, though listed in some dictionaries as a variant of psych, is mainly a noun referring to (1) the spirit or soul, and (2) the center of thought, emotion, and behavior within the human mind. Psyche is pronounced sike-ee.
As a verb, psych (inflected psyched, psyches, and psyching) has many uses. To psych is (1) to put into the right frame of mind, (2) to excite emotionally, (3) to psychologically intimidate, and (4) to analyze. There are also two phrasal verbs involving psyche: (1) to psych up is to prepare emotionally for something, and (2) to psych out is to intentionally intimidate someone. The word is also used as an informal abbreviation of psychiatry and psychology—for example, “the hospital’s psych ward”—and it’s sometimes short for psychedelic, especially in phrases like psych-pop and psych-rock.
Psych can also be an interjection meaning, basically, Just kidding! or I fooled you! In informal writing and transcribed speech, this sense of psych is sometimes spelled sike.
The hours spent psyching yourself up so you’re brave enough to pedal naked through throngs of gawking people. [Seattle Post-Intelligencer]
But the biggest damage might be to the Liberals’ fragile psyche. [Globe and Mail]
Right, I’ve psyched myself up, I’m going to go out there, get in that car. [Guardian]
Saturday was time to check a couple of key Miami psyches. [USA Today]
Psych reports said that in his grandiose and elevated state, Klein would not have known what he did was morally wrong. [Stuff.co.nz]
Military psychologists debate the issue of non-firers, and some say this is because their psyche is repulsed by the act of killing. [BBC News]