An expression of rejoice used in moments of satisfaction, especially to regard something as amazing. Use of this term may make someone, as a side effect, look like a tool.
Theo tried telling Eliza that her hair was radtacular, but she told him to fuck off; he was shaking his hips like a douchebag.
"That's so spectacular, it's rad and hipster. That's... you guessed it! Radtacular!"