Superlative form of wacky: most wacky. (adjective)
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Use "wackiest" in a sentence
"Every Tuesday they invite two celebrities of varying quality to fathom out the responses to the 'wackiest' questions sent to text answering services - including those concerning themselves."
"Are people with Obama-as-Hitler signs, inter alia, not so much trying to make political points as they are vying to be the "wackiest" viewer, the one guaranteed to get on the air of their favorite station?"
"This wackiest of all wacky ideas must have been a trial balloon."