piquete would be something that is cool, it's very much like "vacano" or "vacaneria" and loquera in some cases
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"Eso ta pasao de piquete" - Would be something around "That is off the hook", or ""That is really cool".
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"vacaneria" would translate to "coolness" or "cool" or something around that.
"Esa nueva cancion es una vacaneria" -> "That song is really cool"
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Now loquera could mean the same the other two words
"Esa nueva cancion es una loquera" -> "That song is awesome"
or it could mean that the other person is not understanding what you are doing, so it would translate to something around "weird thing" or "crazy thing".
"Que es esa loquera que tu hiciste?" -> "What's that crazy thing that you did?"
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Do note that all of these terms are ussually not part of formal language, they are used mainly around young people, close friends, or they are sometimes used by uneducated people with everyone.