OTK

Stands for "over-the-knee spanking." It comes from a subculture known as BDSM, SM, or S&M. It is usually used by a Dom/Domme to punish a sub (or, depending on which way you look at it, arouse a sub). Pretty much self-explanitory; a spanking given while the sub flipped over the Dom's knee, much like you would spank a child.
sub: "N-n-no Sir!"
Dom: "What? 'No, Sir?' --get over here for an OTK!"
by Sub/Kitten May 16, 2006
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ROTD

On the social networking/local reviews wbsite, Yelp! ROTD means Review Of The Day, which is the review that most people vote for.
"Did you read the ROTD for San Francisco? I've got to check that place out!"
by Sub/Kitten February 06, 2008
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