An abbreviation for internet chat or message board expediency which is a contraction of the expression "Oh yeah, huh?;" similar to "Oh, really?" but generally meant to be dripping in sarcasm or mock attentiveness, especially when it appears repeatedly.
Chat transcript sample...
X: omg did i tell you robert is taking me to my chemical romance!?!?
X: this is true love <3<3<3
Y: OYH OYH OYH
X: why r u so jealous bitch!