something that is (or tries to be) the pinnacle of masculinity, most often used in regard to phrases, titles, or names
Example 1:

Person A: "What's the most testostertastic name you've ever heard?"

Person B: "I'm gonna have to go with Staff Sgt. Max Fightmaster."

Example 2:

Person: "Sometimes I think video games try too hard to make their skill names tough-sounding. I mean, 'Armageddon Fist'? So testostertastic."
by LilGH June 6, 2011
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