Yike is a singular back-formation from yikes, used as an exclamation of alarm or dismay: Yike, that was close.
It also appears as a verb meaning to express shock or disapproval: Everyone yiked at his comment.
The singular form is less common than yikes but appears in casual speech and online.
1. exclamation — eek, Alarmed exclamation; whoa (Command to stop); gulp (Hasty, large swallow); gasp (Sudden sharp breath); yelp · shriek · oops · uh-oh · crikey · blimey · jeez · yow · gosh · heavens
2. reaction — shock, Violent sudden disturbance; startle (Frighten suddenly); cringe (Shrink from discomfort); recoil (Backward force from discharge); flinch · wince · grimace · shudder · alarm · dismay · discomfort · awkwardness · unease · disbelief